I have a lot of dice, and sometimes I felt my dice tower's tray wasn't big enough, so I made these extenders.
Version 1: a simple, straight extender.
Version 1.1: the same as 1, but split into two parts. I haven't tried printing it, but I think it will be able to fit inside the tower if you wanted to carry it that way.
Version 2a & b: The two parts replace the original tray with two that stack inside one another.
Version 3: Works with the original tray in a similar way to version 2. Has the additional benefit that you can use the tower while the trays are stacked on the bottom. This is the one in the pictures.
All of the trays fit together, so you can mix and match. Combining 2a and 3 will both fit and stack together, but the end will be open.
Since the "stone texture" version of the tower seems to be much more popular than the original, I'm not bothering with uploading smooth ones, but I will if someone requests them.