This is called the "Face Off Backpack".
And with good reason! It features faces only for Sonic & Knuckles...in a face-off position! It's Knuckles vs Sonic as they literally butt-heads in this paint dripping and sketchy-styled design. The red, blue & tan paints are shown 'dripping' from/on the characters faces, which are drawn with sketchy black lines. This backpack has a zipper edge, but no front pocket to disrupt the design.
It's background is plain black, as is the edge & back side. This pack appears in summer of 2017, but where is it sold? Supposedly Spencers' Gifts, but is there anywhere else confirmed? It's refreshing to see an item that's both modern and doesn't use even more of the same/expected stock art. The 'graffiti' drip style may not be for every fan, but this backpack won't blend into the crowd.