Also speaking of which, I do really like your covers ^^
I’d have to check out the guidelines! I had no idea, mostly because I feel it would be so difficult to enforce??
Honestly, I wish novels just came without covers. Just a headache for the writers no matter what we do. Ideally, a writer should just be able to write, instead of agonizing over graphics that would not leave them in the dust.
The MODs here are on a whole different level...Also this community is amazing so its just etiquette I guess???
Well here's the clause in the Terms of Service on the main site, while the general idea is that it applies to the content of a series, a cover technically falls under 'Content' as well and you 'submit' it to the site by uploading it in your edit series page to be displayed to the public on Tapas' platform.
I'll only speak briefly but I'm pretty sure the consensus among most comic artist as well as writers who've been on the site for a while is that art theft on Tapas is simply a no go (plus I'm pretty sure it's mentioned within Tapas' own Creator Guidelines)
This bit
Is pretty interesting because sure a mindset of an indivudual will follow them no matter where the go but a person with sense will realize that if it's not approved or allowed you just won't do it. And sure there are the stubborn type who refuse and continue doing what they're doing (this case being art theft). To be honest I've browsed Novels/Comics that are fanfiction of popular franchises and it's pretty common to find stolen art there but I imagine after communication with one person or another they may or may not change it.
Even as a comic artist I can empathize with this but it's one of the reasons we try to share resources to help each other out (which is kind of the point of a community). There are folks who in some cases will offer to do covers for discounted prices or offer tips and tutorials to better polish ones folks already have.
Plus as was mentioned there's no harm in just asking an artist if you can use their art and if they say no you can try to find another. It's one of the reason's I've stuck with the Tapas community for so long is because for the most part people respect one anothers work. It's just common courtesy.
Edit: and Joanne has shared Tapas' clause in the TOS related to the matter
Well, it's always assumed that an artist is paid (which is a correct sentiment and it's great!), but as a writer, I have never made a single cent. So, as a writer, to have a custom cover, I have to start with paying, while I feel that I will never be paid for hours and hours of writing.
Oh just to add to all this something else I've just thought of that I guess a lot of people don't realise, in my experience most of Wattpad is younger so I guess wouldn't realise, but if you've worked hard on a novel, as most serious writers on Tapas has, you want the best cover possible. Stolen art, and very often it is clear, no matter what the person thinks, screams not a very good novel. It sets a precedent for you as an author, that you're going to cop out and take short cuts, and that in turn makes me think the writing will be lazy. To be honest, I'd rather see a bad or simple cover that's had time put into it, because it tells me the author cares and thought about it. A stolen cover tells me the author wanted to just throw it up. And as an author, I wanted to control every part of my novel I'd worked so hard on, even the cover. Something someone else did for something entirely different just wouldn't cut it.
Since on Tapas covers with people get more attention from readers, you could see it as getting a commission of your characters (so long as the artist know you're going to use it as a cover), and then you can add text in yourself through Canva to make it a proper cover. (if the artist isn't comfortable with doing text, or you want a plain picture) 
Yeah, that's a "lol no" from me, dog. I would never, ever respect a writer who went and stole someone else's art. If you're not an artistically-inclined writer, imagine this... someone just goes and peruses through your words, pulling out whole sentences and paragraphs and maybe even chapters, and then says that "well it describes my character/world/plot the exact way I would, so I'm just gon' go ahead and use it."
The thing too is you can often contact an artist and ASK them if you can use it for a free webnovel. I imagine at least sometimes they might even say yes if you give them credit, or offer you a chance to commission them for your very own cover for your precious baby of a novel. And for photographs it even more common, and they would probably say yes more often or charge you a very modest fee for use of their work. Like... there's no excuse.
This is one of the reasons why I'd like to see more avenues explored for novel and comic cross promotion but that's another topic altogether
Just gonna take a second here to once again sing Unsplash's praises5. Unsplash is stock photography that doesn't look stocky and posed like a lot does. It's all free to use and edit (the love of god guys, please check whether photos you edit into your covers are allowed to be edited or you can get in trouble) without a fee, even in commercial use (again check this because if you get ad rev and it's not ok for commercial use you can get in trouble), with no credit required (although greatly appreciated).
But how many people would read it? In my experience, my books do not get the readership that leads to income. I am on my seventh novel in three years and by now I am disillusioned about producing anything commercially viable based on cold, hard facts. I will always be a niche writer, so Pixabay and Canva's drop on thinggies it is for me.
At least on Wattpad people made covers in exchange for critiquing.
To be honest, I actually never judge a novel through its cover. I read everything I can and I love reading the summary first. The summary is the thing which helps me to decide whether i should read a novel or not, not the cover. Just need a basic picture you can take out of daily life and put it with a nice and artistic word font. That is enough
If only everyone had this attitude, we wouldn't have this discussion, heh. Alas, covers are what gets reads.
There's nothing stopping you giving that a go here. Look at threads on here that just go "plz draw my character" and get it. And people are desperate for reviews around here. If you made a thread saying "I will review your comic/novel if you make me a cover/draw my character" well the worst that'll happen is no one will do it and really what will you have lost? Nothing. You'll be no worse off than you are now.
I haven't seen people doing it here, so I assume it is not done. Also, I don't even know how to start critiquing comics. Not being an artist or having had read many.
If you do a bit of searching there's been a good handful of "I'll draw your OC type threads" (although they've probably gotten buried by promo threads) but there's really no harm in trying to see who bites for a "reviews for covers" type of exchange thread all you've gotta do is try
Hence why a lot of people's advice when it comes to creative pursuits like comics and novels is to create for yourself first and foremost. Because making something commercially viable is a monumental task, and a gamble. Even if something looks like it can work on paper, life is unpredictable and it can turn out to be a flop.
Like all of my work comes out of my love and passion for each story. Sure, any money I can get from it is nice, but even if I never saw a cent, I love my characters! I don't mind dropping like $50 to get an awesome drawing of them. (my ipad's lockscreen and background for example are images that I commissioned from an artist 2 separate times. I just love their style and how they depicted my characters.)