Yeah I would actually really appreciate a separate section like that for characters, extra art/sketches as both a reader and a creator.
From my point of view as a reader, when I'm a fan I'm really into character profiles and extra sketches and sneak peaks on the side. To be able to easily get that on tapastic (separate from the comic to avoid interrupting my reading experience, or attempting to scroll that dreaded mess of backlog that can collect on the wall) would be absolutely great, as to get those extra tidbits for webcomics as it is now I need to follow the artist outside of tapastic on their artist social networks, which more often than not, gives me a whole bunch of shit I don't want instead of the stuff I do want. The most prominent examples being reblogs of memes, funny pictures or other none art related things, or when artists I watch join in on some friggen twitter chat. I just want to see the extras and and sneak peek sketches, I don't want all this other shit! I just want the stuff related to your project or your artwork. (Don't get me wrong, I have no problem with artists doing whatever they want on their social media pages, I mean it's yours, it's just frustrating when I want those specific things and there are no other options for me to get them.)
From the point of view of webcomic artist, yes, I would love to include this optional side stuff, (concept art/sketches/sneak peeks, character profiles, FANART) but don't really want to (or have to be careful when) throwing it into the comic because it could both break the flow of the story (even at the end of a chapter depending on how much stuff you put in there) Right now the best option is to make another comic series dedicated to extras of your current series, and I a just HATE those, because there's really no way to organize all your extras, and making separate comics for all your different kinds of extras is pretty damn excessive and well... messy.