NPC/Entity Spawn Icon Creation

Hello,

I often create NPCs and Entities in Garry’s Mod. But when ever I finish something and use it in-game, it always bothers me that the spawn icons are purple and black checkerboards. I’ve heard making a spawn icon is easy but I have an extra limitation, I have a Mac. So if anybody out there knows how to make a spawn icon using only Mac software, please let me know via this thread.

Thank You,
Stealth SEALs