I also like painting in the 4x4 art squared format. There is even a group of artists doing 4x4's in Yahoo and Ebay. I joined both groups because I liked the larger size format. I tried doing ACEOs but found the surface too small for my taste. The following are both original mini paintings done in acrylics on 140 lb. watercolor paper and they're only 4x4 inches. Both are currently for sale at www.artbyus.com
and "Blue River Mountain"