Maybe a hognose or kenyan sand boa might be something to look into? With both species the adult male stays significantly smaller than the female, but even those don't grow too large. They both also have kind of unique 'looks' compared to a lot of other common pet snakes. I mentioned hogs before a little and why I like 'em personally, but kenyans are adorable too. I like the way they bury themselves and leave their little heads poking out. They do come in a couple different morphs, though I'm not familiar with many of them. Hognose do as well, but many of the morphs are on the pricey side right now.