If you want them to go away you need to upload a single black canvas to your textures. Since all texture items need at least one coloured pixel in order to be visible a completely black image will appear invisible.
If you can't get them to appear in-game there are a few things you can try:
- Change the file extension (eg, .PNG, .JPG, .TGA)
- Play some games online.
- Try "/download UncleLeo1"
- Exit your Toribash client and re-open.
- Repeat steps 2 to 4.
It should be working out after that, it takes it's time, be patient.
ps. I uploaded a black canvas in attachments for ease.
Hope it works ;)