Are your sprites the right size? Check them all unless you are sure - one may have to few/many rows or columns.
Do they need a mask, or not?
Are they in the correct screenmode or bit depth?

Have you stored them in the place it expects, and the right name? (if you don't need to drag it onto an icon, that is.)

If none of this helps, perhaps you could say what error message you get?

I remember fiddling with Infinity on the BBC, it was lots of fun although I always wanted to put in more code than the memory available.