I just made my son a queen size quilt using a wolf panel
42 x 36 in the middle and then blocked around it until I got the size I wanted. The panel was like 6 or 7 dollars I bought it on 4my3boyz website.. I was very happy with the panel and they had a pretty good variety.
What your doing is wonderful... I did see alot of different panels when searching for his. I googled fabric panels.. they do sell some on amazon also.
Good luck