You can identify the enemy and find out the info you need on it by hovering over the enemy while the game is paused.
As for why there aren't wiki pages about them, that comes down to the fact that we just don't have time for that. If you or any members would be interested in doing that, let me know and I'll get you wiki editing access.
That said, adding any pics for that kind of thing would be premature right now, as all the graphics are going to be changing.
Aye, I've had the idea of doing this very thing myself, but the changing art is the reason why I havent. Particularly since some aspects like enemy/boss size might also change, which might entirely change how the monster in question works.
Be pretty silly to write all that up, get it finished, and then BAM art update done and suddenly none of the pages make sense anymore.
Once that's done though, I could probably do most of this, if there seems to be enough interest/reason to do so. I do think having a "bestiary" section or whatever on the wiki makes sense.