The following shows up in my log.

67.100 Warning! Sprite at {0,0; 64x64} from ammo-loader/graphics/icon/chest.png is defined with 4 mipmap levels, but level 1 is expected to be at {64,0; 32x32} which is out of bounds of the source image.
67.100 Warning! Sprite at {0,0; 64x64} from ammo-loader/graphics/icon/chest_b.png is defined with 4 mipmap levels, but level 1 is expected to be at {64,0; 32x32} which is out of bounds of the source image.
67.100 Warning! Sprite at {0,0; 64x64} from ammo-loader/graphics/icon/chest_r.png is defined with 4 mipmap levels, but level 1 is expected to be at {64,0; 32x32} which is out of bounds of the source image.
67.100 Warning! Sprite at {0,0; 64x64} from ammo-loader/graphics/icon/chest_y.png is defined with 4 mipmap levels, but level 1 is expected to be at {64,0; 32x32} which is out of bounds of the source image.

Thank you for using the mod! And thank you for reporting this!

Unfortunately, I have absolutely zero idea how the graphics side of things work. The sprites in question were provided to me by a graphically skilled fan of the mod to replace the ultra-basic sprites I was originally using. So long as this doesn't start affecting the mod in-game negatively, I'm inclined to leave things as they stand.

Don't hesitate to report any other issues!