Today I have a 4.25" square card and some "homemade DP", I started by cropping down "Inspiration Mosaic" on one end and then ran a black marker along the cut side to give it a new border to match the other sides. I used a greeting and most of the images from Rupa's "Are We there Yet?" set in the blocks.
I put the greeting into a box that fit it nicely and used the dashed and straight line below it to make the space more like a square and then the line, dash, line below kinda looks like a road, no?? Since I wanted to fill every space I just masked off each area with Post-Its, just lining up the sticky edges with each border and stamping each image with Memento Black onto Pure Luxury White. (Most I only had to mask on two sides but a couple I masked three...) I chose which image went where based on their sizes and to alternate them going in different directions. I love the finished "on the go" look! I matted it on Rocket Red (edged with black marker)and popped it up onto the base weight Pure Luxury White card. The greeting square is colored in red to match.
I hope this gives you some ideas about how to create DP with several images from a single set for a totally coordinated background and how easy it is to make the quick change to a square! (Next I'm going to give my grid a well-earned rest LOL!, and share a card using just shapes for a super cool pattern, I think you're gonna really dig it!) :) Stay tuned! Keep in touch! ;)