Every time I changed one of the stage's portrait in the stage selection every portrait becomes grey and glitchy... Why does this keep happening?
What is the file size of the portrait.
Look at the normal size of the portrait, and take a look at the one you made. Are the sizes for both proportional? If the original size is like... 500 X 500. Is it the same, or proportionally the same? If not, you'll get glitchy textures.