Custom Backgound Resolution Question

So I’ve been trying to make a custom background for Gmod using an in-game screenshot. My monitor resolution is 1600 x 900. I’ll take the screenshot, go into paint, resize it to 2048 x 2048, make .vtf and .vmt, and place it in the necessary folders. Pretty standard stuff.

The only problem is that the game annoyingly resizes the background to fit your screen resolution, which obviously lowers the quality. If there any way to create a background material that is similar in quality to the default Gmod one? I checked out the .vtf file and it’s exactly the same size as the screenshot I was using, and I know the quality can’t be any lower as mine was a print screen on highest settings.

Better yet, is there a way to make a texture work in Source that’s dimensions aren’t powers of two (so I could just use the original image size)?