Must you piece them? I'd simply purchase a really nice " pawprint" fabric.

Since there are only 5 pictures of those cuties, I would find another block pattern to fill in the other space. If you did 9 Blocks, each block 20 inches square (so if no border a 5 foot x 5 foot quilt). The outside corner blocks and the center blocks would be the dogs. They would get a border to make them 20.5" unfinished / 20"finished. The other four blocks could be any design, but I saw this cute free pattern by Moda ( http://www.unitednotions.com/fp_here-boy.pdf ). 4 of the blocks (2 of the square and 2 of the bones) make an unfinished 21.5" block (20" finished). Those four blocks would be the top, bottom, and sides.

I drew a quick picture:
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Where did you get those beautiful prints of yorkies? I would love some of those.