If its on an upper floor maybe you could install a sky-tube in the roof?

Also called solar tube skylight. Look on here for more ideas. Good luck.

Changing the wall color would be one of more economical options.

You can purchase mirror tiles with strong back sticky tape and place them over the tiles. This will have the dual purpose of bringing in more light and disguising the red tiles. With the black you could turn it into an Art Deco lookAlso remove the toupe from the toilet cover please. And change the carpets/mats to black or white or best, black and white

I like the tile. Above 2ft is it all white tile. It would be nice to see the vanity or sink area also to get a better judgment on how it looks.