I get the standard pink and black missing texture on all blocks and items except the Nether Bomb. As far as I can tell, I didn't do anything different with the Nether Bomb and the other blocks (other than the different textures) and I made sure all of the textures were .png.
By the way, why can't we use .gif's anymore?
Issue comments
The textures seem to be in the format Minecraft does not support. Go to forge\src\main\resources\assets\minecraft\textures and open these textures in an external editor (I used gimp) and just save them in png again so the format gets corrected. I did this and it worked.
The textures of the blocks that have missing textures are gif, for example, your NETHER block uses n.e.t.h.e.r..gif file, so it is a gif. Minecraft only supports png format and even MCreator does not even let you import .gif directly. Convert your textures to png format and select them for the block again. And avoid strange file names as n.e.t.h.e.r. as this can cause issues too.
If you would like to use an animated gif, import it in animation maker in MCreator which will convert it in a proper animated strip png format.
I have converted your nether block texture to png and imported it in MCreator and selected it as a texture and everything worked as it should.