You probably forgot to install the interiors properly. Can you describe exactly what you did? Additionally, can you specify where you got the levels from?
In MBP 1.50, on a Mac, you should go to your home folder, the Applications folder (which should have maybe 1-2 items normally), and then right-click the MarbleBlast application and "Show package contents". Another folder should appear. Go to platinum, and then data. You should place all custom levels in the "missions" folder, and all custom interiors in the "interiors" folder.
All interiors are files ending in ".dif", or image files that are usually square and/or looks like a "texture"; this should be almost all of the image files. The level in itself (mission) ends in ".mis", and usually has a matching level picture with the same name, but ending ".png" or ".jpg".
If the custom level you are installing are already divided into "interiors" or "level" folders, then simply copy the contents of "interiors" into the "interiors" folder inside the game, and the contents of the "levels" (or similarly-named) folder into the "missions" folder in the game files as well.
I may be wrong, as I haven't actually practiced any of this in MBP 1.50, but just using common sense and prior knowledge. Once again, it would help to have a description of what you did.
Finally, in the base folder of the game, there should be a console.log. Run the game and play any levels with missing interiors, and then immediately copy the console.log, and attach it by first archiving it, and attaching the .zip file to your post by clicking "Reply" or "Edit".
I hope this helps.
IN BRIEF
1. Open Package Contents of Marble Blast Platinum.app in ~USER/Applications/
2. Navigate to platinum/data/
3. Copy interiors into "interiors/", levels/missions into "missions/"
4. Run the game again, start playing each of the levels.
5. Quit the game.
6. If you saw missing interiors:
-- a) repeat the first step,
-- b) Copy the console.log file to the desktop
-- c) Go to the File menu, and Create Archive.
-- d) In this topic, click "Edit" in your first post.
-- e) Attach the console.zip file you just created, via "Add file"
-- f) Submt.
7. Make another reply describing what you did before, if you can.
(That looks better.)
~ PM
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