Okay, wait- what's the plan with these putative Christmas lights? To string them around the edge of the sign behind it to create a lit "frame" around it?
'Cause if that's the question, forget about sourcing LED lights and just get a bucketload of plain old mini-twinkle lights. I have several strings of those I can donate (I'd rather keep the LED ones I have) and I'm sure many others do, too- not that it matters, because if the total distance around the outside is 48', and we recess the strings by, say, one foot to improve the diffusion of the light which reduces the length to 40', two or three strings is all we need.
I know, fire safety, blah blah blah, but realistically, there is ZERO fire danger from normal twinkle lights over LEDs. If you can indefinitely touch a twinkle light to your lips after it's been on for 2 hours, it isn't going to cause a fire. Ever.
If, on the other hand, the idea is that we use LED twinkle lights to cast light down the face of the wall to provide lighting for art hung on the wall for the show, well, you can use my lights, but my expectations for success there are pretty low. Twinkle lights are designed to be highly omnidirectional and lighting like this really needs something designed for a much higher directionality. Might be a fun project to try, though.