You must ask the owners of these files the permission to borrow them, you can't simple borrow the sprites, sounds, etc. without asking the permission of the owners.
@ Rk0Z: Please note that simply making a thread with a poll is NOT sufficient to get the necessary legal permissions unless all involved original file authors reply with a positive message. It's probably better and easier to send PMs to all original file authors as already stated by others here.
That's because only the creators of files have the rights to decide what happens with these files and nobody else.