Various GZDoom Questions

1. Are you sure you added the PNG textures to the patch table in SLADE? If not, then some texture won't be available in Doom Builder. (I don't have that much experience importing texture though so it might not work.)

2. There is a good video tutorial by Chubzdoomer about how to adding and making custom monsters and things through SLADE. Here it is:

3. I don't think GZDoom will work without an IWAD, atleast in my experience. If you run GZDoom without an IWAD, it will simply refuse to run telling you that you need an IWAD to use it.

Can an IWAD be created from a pk3/zip file or does it have to be a "proper" IWAD?

I've never tried this before so I'm guessing it'll probably not work.

"IWAD", in Doom engine terms, is just the main data file for a game. So basically when people say "IWAD", they generally use it in a way that's a synonym for "game". E.g., "requires the Doom II IWAD" means "requires the Doom II game".

Can you play without an IWAD? ==> Can you play without a game? No. You need a game to play if you want to play a game. That's obvious.

Can you create a custom IWAD? ==> Can you create a custom game? Yes. There are many examples of people who made a custom game using GZDoom as the engine. You need to provide all the data required to make a game that works, though.

For textures, just add it to a .wad file and then set it between F_START and F_END for flats or TX_START and TX_End for walls.