We have 2 Bearded Dragons (16" & 21"). Normal size is about 18". They're really mellow.

We just bought a Blue Tongue Skink at the White Plains NY herp show yesterday. They're supposed to be real mellow and normally grow to about 18", max 24".

We recently got an Argentine Black & White Tegu. They're supposed to be one of the most intelligent lizards. Unfortunately they're a little out of your range, they grow to 3.5 to 4.5 feet long!!