What do you think? Would it be a bad idea and look weird? Or, would it be interesting?
I think it would look wierd. But then again its diffinatly worth a go. Try makin a bg in 300 x 240 then double its size in gimp or photoshop then try a hi-rez sprite on top.
Though I do think that it would look better the other way around with higher rez bgs with lo-rez sprites on top. For some reason I think "the Dig" might of done something like that. Though I'm almost certainly wrong. ???
BaRoN's game "Charlie Foxtrot & The Galaxy of Tomorrow" did this, and I think he new MAGS game also uses the same technique. Lots of people commented on it, and said it wasn't a good idea, but while playing the game, the effect seemed to come off okay.
You can pretty much find this out by taking any game that runs in 320x200 and has scaling enabled; run it in 640x400 and the sprites will have a higher resolution than the background.
This tends to look better than running it in 320x200.
I'm doing something like this, and it didn't turn out that bad. Just have fun with experimenting.
As long as it's consistent in its inconsistency, that could be interesting. The inconsistencies in Charlie Foxtrot niggled me a little. For Nelly Cootalot I used characters and backgrounds in entirely different styles, and I liked how that worked. I guess resolution is part of an images style.
I agree with GreenBoy however, that low-res sprites on h-res backgrounds might be more fun.