While I was browsing through Sonic stickers like I usually do every Tuesday morning, I found some pieces of artwork which SPURRED my interest. They are the Tails, Sonic (under Tails), and Shadow ones. So I am wondering what game/etc they are from? I do not recall ever seeing them before.
The Shadow one is, accordding to The wiki from the Sonic Art Assets DVD, but the other two ya mentioned, I couldn't find at all.
Never seen them before. I know the Knuckles one isn't new or anything, but it still looks different. I always thought that pose had him smiling... Anyway, it says 2010 on that thing, so they might be relatively new.
Knuckles has a non coloured version in the channel site: http://sonic.sega.jp/SonicChannel/enjoy/coloring/001.html (4th of the second row) Same for the Sonic one: http://sonic.sega.jp/SonicChannel/enjoy/coloring/006.html (3rd of the first row) Never see the Tails one, but there is a similar one: http://sonic.sega.jp/SonicChannel/enjoy/coloring/004.html (4th of the third row) It's the Chronicles one. Similar, but not the same, you are right.
The three on the left definitely are, but I don't think I've ever seen the three on the right before. ..They're probably new?
The Shadow pic isn't new. I recognize the shadow one because it used to be Aquaslash's avatar (except that the black was recolored as yellow to emulate his super form; I had actually thought that was the official artwork...) The other ones I know I've seen somewhere; I can't pinpoint it.
The Tails art is a cleaned-up version of the Feb 08 Sonic Channel wallpaper. Shadow was originally released for SA2:B but I can't seem to actually find the damn thing anywhere. No clue on the Sonic.
So they are all from Sonic Team's digital colouring book. OK. I am glad the option exists to purchase these as stickers rather than printing them off to colour on one's own time.