Depends. . .
I believe if it is non-toxic to humans it should be OK for snakes. Acrylics are basically plastic anyway, which is commonly used for all kinds of snake needs. However, if it is an artist's acrylic, or even a latex house paint, humid conditions over a period of time could cause the paint to start peeling off if the surface of your box is smooth. So, you could either sand the box to make a rough surface for the acrylic to hold onto or seal it with a water based polyurethane to be safe. Or both. I find acrylics very easy to peel off of silky-smooth surfaces like plastic, so maybe a shedding corn would, too.
And while you're at it--you have a knack for art-- you should think about painting the outside of the hide box, too. I'm sure that your new baby would appreciate having a beautiful, as well as cozy home!!