With the help of the knif take off the color pieces of the rubik. If this is too hard and the color pieces comes squared you could skip this step
this is how the rubik looks like when you take off all the color pieces.
With the help of a software fit the images you want to use in the measure of the rubik area. (I did it in corel but you could use any program you know or even just fit one side and cut the rest of paper later)
Print the images. I used photographic paper because of the gloss and the thickness of the paper.
With the scissors cut the paper in lines
Use the double sided tape or the glue and start to stick the photos.
if the pieces of paper don't fit so well cut the extra with a lot of care. Be pacient in this part, at the end all the work will worth it.
Use the x acto knife to cut the excess paper.
At this part you could use the glue. To cover the paper and keep the photos clean.