I presume the game isn't going to be commercial. If it is the completely ignore this post.
I myself am crap at graphics, but can offer some advice.
There always seems to be talk of projects where musicians/coders/graphics people are needed but in most cases the game/demo or whatever is just a concept in somebodies mind or maybe even drafted on paper.
Therfor at present your post is likely to be ignored by the majority, 1 because your description is very vauge, and 2 because you are a new member and why would somebody help someone who they don't know and owe no favours with such a major undertaking. It's not like you are asking for a game request here - this is something that will take at least a few hours of someones time.
You could upload a basic version (if you have) of the game to The Zone or maybe even just put down some more detail here to show you are really serious about making this game.
If people like what they read/see (by that I mean the playability/scope for enhancement) then I am sure you will get overwhelmed with offers as we have many talented graphics people here.
I understand you might be unwilling to share the unfinished project, that I am fully aware of, but to be honest this is the only way I think you could get what you are requesting.
Other ideas are of course to find many of the free game sprites available on the web (OK, most are crap) or even rip the graphics from a fave Amiga game for now.
Don't take my post the wrong way, I am just telling things as I see them. Anybody developing anything on the Amiga these days deserves a pat on the back, and I see from your age that you probably weren't an Amiga owner during it's hey-day and I fully applaud you for even thinking about developing something for such a nice machine rather than go the Micro$oft/DirectX/PC Game Creator route.
Hope you find the help you need, hope some advice here was useful