As already mentioned the puzzle pieces would be great whether it is an autism awareness quilt or one for an autistic child.
If it is for an autistic child I can tell you what DGS likes - which does not mean all autistic kids would like the same. He likes fleece, flannel, silky (really likes this because it is both cool and smooth), leather or vinyl, suede, bright colors, puzzles, anything with wheels, cuddly things, no tags in the neck of his shirts to poke him, things to chew on, letters, numbers, words, pictures, repetition.