Get a custom matte for your artwork, so that the artwork when matted will fit with a ready-made frame, i.e. 16x20.

I just had 3 pieces matted--$38.59 each (double matte). I just googled some frames and I can probably get something nice for under $20.

So, I will have custom-looking framing and matting, for about $60 total which for anyone who has done custom framing, is a fraction of the price, as you pay by the linear foot.