I just finished 4 T-shirt quilts for my grandkids; however, their shirts had different sizes of logos so I didn't go all the same size blocks. I did sash them in a dark gray which was very neutral and let the blocks do the talking. With each one I picked a color that brought out colors within the blocks and on all but 1, I used the same color as the backing.....Have fun with it!!!

Just thought of another question . . . should I stabilize the quilting fabric I use for my sashing and borders, just like I did for the t-shirts?

I would sash in black as this would highlight/accent the black in the T shirts - and I would only use one color to sash. I would suggest you go with your instinct and you will be surprised at how nice your quilt looks!

Gray is a great choice for t-shirt quilts - it does the job and often times does not compete with the t-shirt colors. There are so many different shades of gray - it is fun to see which one gives you the effect you wish to achieve. If you want to use black in the top - think about adding a border that is black. Please show us the end result - would love to see it!!!