Ed Harvey has made quite a name for himself on the Paint.NET forum by consistently releasing some of the best and most comprehensive effect plugins. He has just released an updated version of his effects plugin pack that supports Paint.NET v3.20 and uses some of its IndirectUI capabilities.
I highly recommend this plugin pack, so go and download it! In all, there are over 20 effects that go into the Blurs, Distort, and Color effect menus. Here’s a preview:
Original (Olivia Wilde)
Dents (one of his coolest and most popular effects)
Multi View Warp