I think that a braid pattern might be really busy unless you put a plain strip between each figured piece. I think a charm pack would be your best bet - there are usually at least 2 of each fabric so that you could do the matching game as Nan suggests. I've made several I Spy's and the feature fabric has ranged from 5" to 7.5" squares depending on what I had to work with. Have you done a Google Image search for I Spy Quilts? There are a lot of pattern ideas.