S.Casale is correct. All you need to do is upload all your greatest images to that specific Visualize Forum thread. Doesn't have to be 20 images all at once - you can space them out in order to get feedback from the community on each one.
Each year, I scan through that specific Visualize Forum thread for our favorite images, and then reach out to the creator to incorporate into the splash screen images for each new release.
Can't wait to see your images!
Product Manager | SOLIDWORKS Visualization