Thanks.  I try to pick a standard width that works with most of the shirts, so I can keep even columns.  but then I trim the height as small as possible because I almost always are trying to sqeeeeeeze in as many shirts as possible.  ON this one I have another 10 that wouldn't fit.

I did one where I optimized cuts of the images, put black borders on them all then laid them out pleasantly into 3 general columns. I then added side sashing in the persons favorite color to blocks that needed to be wider to fill in that column. Assembled the columns trimmed straight up and down and sewed those together. Looked like framed pictured on a "photo wall".