GM doesn't bundle external resources at all though, they're openly accessible from whatever folder you store them in. I don't mind people using my sprites, but being able to hide my dungeon map images would be handy. 
I found a way to do that! it's actually really easy, but kinda hard to explain. Open up Terminal in your applications folder (it should be in the Utilities sub-folder)
now type in 'man chflags' skim through this, especially the section about hidden, and nohidden.
without the quotations. put the folder in your desktop, and type this:
chflags hidden ~/Desktop/Gamefolder/*
okay here's the tricky part.
type in: cd ~/Desktop/Gamefolder/
then: ls
okay so you should see a list of all the files in your folder, just so you have a spelling reference.
alright, now type in: chflags nohidded ~/Desktop/Gamefolder/"name of what ever thing you want to un hide"
If there is something with a name that is more than one word or contains the & sign you'll have to surround them with parenthesis.
If you messed something up, and want to start again, no sweat. This code is the best Unix code to start with, it can't screw up your computer, but is a gateway to letting you screw it up.
okay to reset anything you've done type in:
chflags nohidden ~/Desktop/Gamefolder/*
capitals aren't needed
If you want to learn more type in 'man man' or 'man less'
but the manual expects you already know the commands, so just google Unix Executable codes, or just Unix (most people just cal it Unix.)
Hope I could help, sorry I wrote so much  :-/
