The OMGosh quilt is pretty much all about the piecing. Custom quilting could be done on it but because the piecing is so small you would have to ignore a lot of it and that may take away from the impact of the design. I would recommend finding an all over panto that you like and using that. You can view panto designs on line by doing a google search of panto designs. Here is a good source to start with:
http://longarmquiltingsupplies.danem...y/pantographs/
If one hit my rack I would choose a fairly open panto, unless the piecing required denser quilting. I have had a few intensely pieced quilts (FWS) that required closer quilting because seams were missed or coming apart on the piecing so dense quilting was required to keep it together, quilt down fullness, etc.
A few other options for this quilt would be a simple straight line quilting done in a grid that bisects the 9P blocks that form the "irish chain" in the quilt; an all around all over design that seems to work on every single quilt I have seen it used on is the Baptist Fan pattern.
Edited to add, diagonal straight line quilting on a LA is more difficult than on a DSM so if you are going to send it out for LA quilting don't be surprised if that option is more expensive for you. You could do it yourself on a DSM with a walking foot. I think a panto, all over freehand feathers or swirls or baptist fan design would be your best option for LA