I have seen some beautiful quilts that only used 3 fabrics.
You can make your charms any size you want. People usually use 5" squares because that's the size in a charm pack.
1/4 yard is only 9" wide. 1/3 yard is 12" wide. You can get 12 five inch charms from a fat quarter, but only eight from 1/4 yard.
Look at these quilts for ideas:
https://www.google.com/search?hl=en&...46.jHeA2jA1Uik