I like the images. I don't want artists to put tons of extra time drawing something special for me -- I know that's time consuming! I want artists to spend time on their comics, not making special asides when even a simple thank you image will do. To those that go above and beyond, I salute you; to those that post simple thank yous, I am still very happy to get them! I am also from inkblazers, and I felt posting the thank you was common courtesy unless the author specifically stated in their profile to NOT post a thank you … otherwise I felt I was ignoring their interest in my work. Surprising, fun conversations can start up from that simple act of just saying thank you.
When I first came to tapastic I was surprised by those images, but a friend taught me about the norms of tapastic and I jumped right in. I am sincerely grateful for every subscriber, and taking out that moment to go to a new reader's profile, read it, and check out their work is fun. As I said, that simple act can be the open door to conversation.
And yes, it can be a way to get new readers. Thanking someone on their wall for their interest is kind of a way to get more exposure, but if you sincerely like that comic, wouldn't you want to help that author get more exposure? For a lot of us word-of-mouth is really our best (and for some, our only) advertisement. The more people that know about our work, the better. Artists, don't ever be ashamed of advertising your comic! Just do it within the norms of the site you belong to -- do not post a thank you every time someone likes or shares an episode; don't spam non-reader's walls with invites to read your comic; don't jump into conversations on other people's walls to advertise your work; so on. Do post in the forums (hey there!), on your own wall, etc.
And yes. I find comics this way. I like fantasy. I draw fantasy. If someone likes my comic, I will check out who else has thanked them! I always make sure I did not thank them already as well so I don't bombard someone with images.