Well it only takes a few moments to take the frames apart and swap in your own images.
Step 1: Step 1: Make and trim replacement prints
The trick is sizing your prints to that dimension, and then adding white canvas space around the images, turning the digital image file into a 6.85" square image, with a white border extending to 8x8 inches. Then add more space on the sides of your digitial image (say with photoshop?), turning it into an 8x10 standard print size. * Then send your images to the local online photo printer as 8x10 prints.
When you are ready to hack your Ikea frame, simply trim the prints to the 8x8 inch size.
*I usually add the extra width space in the last step as pure black, to balance the white border around the print. That way the photo printers wont darken my photo if they auto adjust the printing to mid-tone grey.