Files you can download for personal use are in the Free Laser Designs category. If the file is for sale there will usually be a mention of it in the original post or they will place a link to their etsy, or other, store in their description (just click on their name.)
There are at least two paint rack designs in the Free Laser Design category:
And one for Sharpies
Once you have cutout and assembled a couple you will probably see the basic principle and how you can design your own. They are basically boxes with holes in them plus some method of racking or stacking them.