The arrow entity texture is found in "/item/arrows.png" I had this same problem at first, because i figured the arrow entity was using the texture from the items.png file, when actually it has its own graphic file.
The arrow entity's texture is defined at the top of the RenderArrow.java file. For your projectile, just do as they did and replace
When it appears in the game it is just a white box.
How do you add textures to the entity?
SOLVED!
The arrow entity's texture is defined at the top of the RenderArrow.java file. For your projectile, just do as they did and replace
with your own file, like...