From what I can tell, a shape is an entity used in all the Marble Blast titles. I noticed that the mod Marble Blast Powered Up added some more new types of items. Would it be possible to copy the shapes and sounds used for the shapes from Marble Blast Powered Up, and simply put them into Marble Blast Gold?
Yes. Whirligig allows MBPU's code to be re-used with credit to him and HiGuy, and I expect this is also true for shapes and sounds, although I would ask to make sure. MBPU has
a remade power-up system
for modding purposes, so the code for it is a bit spread out.