My adult son did a Kickstarter for some stl files that was for a modular model paint holder system. He is into Warhammer 40K. He asked for my help when he got the files. They are crap, a 2 piece part that is held together by 3d printed straps and 3d printed straps that interlock multiple blocks. the straps didn't work, and the whole file was a mess. So I hopped on my computer and came up with a single block that can hold 3 different paint sizes ( need an extra insert in hole for smallest bottles ) and it has 2 holes in two directions for 3mm threaded rod. The rods screw into the green bases then parts drop down on them. 24 units fit on a single base, then multiple bases can be connecter together. It could go higher, but that was the longest 3mm all thread I could get easily.
David