I know a bit about the Amiga, but not enough to tell you how to extract any data from an Amiga game. The best place to start would be to read up on how the Amiga rendered games and what tools and file formats were commonly used. The Amiga had a well known art program called Deluxe Paint, which was comparable to Photoshop. There were probably a number of other programs and file formats used too.
As for compression, most Amiga games came on floppy diskettes and were rarely installed to the hard drive, so some form of compression is likely. It's also possible that some games didn't use compression, however. Game designers of the day knew a lot of tricks for squeezing graphics and sounds from the system, and the Amiga was only capable of 32 or 64 color palettes before the AGA chip was introduced. That would probably explain why the sprites you have are so small: they are probably small in pixel dimension and use a palette. Even if a game did use the AGA chip, it wouldn't make the file size much larger.