Oh I love Paint.NET! It's really cool that you're able to make such great textures with it!
It might be possible to emulate the .NET framework but I've had so many problems with Windows emulators that I don't even bother at this point. I'd recommend looking into it yourself though, because there are a lot of benefits from using Linux. The only problem are all the software limitations, especially the ones I hadn't thought about, like the fact that Microsoft owns the H.264 video standard, etc. I'm about to rebuild my PC and set up a Windows & Linux as dual-boot for this reason.