The way to fix things like textures not working in MBG such as space or mud (which were deleted from MBP) is simple. It also affects the end game gui, and many other things.
Here's how to fix this issue:
1) Go into the marbleblast folder in library. Load the marble folder.
2) Go into data from there, and rename the init.cs.dso to init1.cs.dso. Then, load MBG and play a level it should make a fresh dso called init.cs.dso in the same location, the marble folder. Move that into the corresponding folder in marbleblast gold's package contents. Then, load MBP and again play a level and it should make a fresh init.cs.dso in the library location. Move that to the corresponding place in MBP's package contents.
3) While still in the marbleblast folder in the library, go into marble-client. From there, rename the scripts folder in that client folder to scripts1. Then do the same steps as before: load MBG and play a level and a fresh scripts folder should be made. Move the dso's made in that to the corresponding scripts folder in MBG's package contents. If a new scripts folder is not made for some unlikely reason, rename scripts1 back to scripts, and go into the folder and delete the files. Then load MBG and play a level and new dso's should be made and move them into MBG's corresponding folder in package contents. After doing this for MBG, do the same for MBP (load MBP-fresh copy- so on).
4) Go into marble-server and rename the scripts folder in there to scripts1. Then do the same steps as before for this scripts folder. When moving to corresponding places, make sure you are in the right scripts folder (remember one is client-scripts and the other is server-scripts).
Enjoy the new perfected MBP!
~Tutorial made by Perishingflames