I think I wrote some code to have unlimited sprites, but I'd have to go back and check to be sure.
As for the icons, OS X 10.6 no longer displays the old style icon resources, so it just shows the default application icon.
OS 10.6 will still display "icns" resources - because if you use the Finder/Get Info to paste your own picture onto a regular old text file, it will actually create a resource fork with an "icns" resource to store the icon. Another way the resource fork is
still used - if you set a document to open in a specific program using Get Info, the Finder will add a "usro" resource.
So, we can convert all of the 8-bit icon resources into "icns" using
Iconographer. GM would still have the 8-bit resources to display in the icon chooser (because displaying an icns requires different code) - but when it compiles the game it would put in the "icns" instead. This would fix the bug and only require a small change to GM which still seems to work fine otherwise in 10.6.