Well I don't know anything about time limits or debts (other than my own, of course). But I do know that I've seen much better work from Art Instructor. This diorama would be pretty good for me, but AI can do a lot better than this. We've seen it.
There are seams on the muzzle, the decals are silvered around the edges, and there's little or no tie-in between the StuG and the groundwork (dirt, grass, pastels, etc). The figures look like plastic toys, mostly because of the way they're positioned.
I normally wouldn't point out these things, because in some cases they're the kind of thing I would do. But I know that Art Instructor can do a lot better than this one.