I found a flash drive with all of my artwork from the last 8 years on it. I'm slowly going through it bit by bit just for fun. At some point about 5 years ago, I made my first 18x24 sized poster and fell in love with that size. Most artists seem to gravitate to printing 11x17 but I personally hate that size. The bigger the better is what I say. 18x24 is my go to working size for art projects.
