Diamonds work fine in the original release from Sledmore, I think the files are still on HabboFiles, use the database provided in the emulator download.
all you do is open external_override_variables and near the top you should see something like diamonds enabled=false im assuming its set as so just change it to true then restart emu.
Correct, and for the other fix - Im not sure if this will work. But if you get the HEX or w/e colour code of the purple, search it in UI Editor, you should find where the code for your now Pumpkins is. Just go ahead and edit this.
To change the image of the star, use a SWF Decompiler, find the image of the star, and just replace it with the image you want.
If you need anymore help, shoot me a message