I consider myself to be spastic when it comes to my computer's wallpaper.  I am constantly changing it from one image to another on almost a daily basis.  How do I constantly find awesome images, you ask?  Well, I find my images on Reddit, in a variety of "porn" subreddits.  "Porn" has a different meaning when on Reddit, it means something along the lines of "beautiful imagery."  You can find subreddits like 'EarthPorn,' or 'CityPorn,' or 'HistoryPorn.'  Each subreddit is full of hi-res images that work perfectly for wallpapers.

Elemental Wallpapers

Imgur via Reddit

Synthetic

Imgur via Reddit

Organic

Imgur via Reddit

Aesthetic

Imgur via Reddit

Scholastic

Imgur via Reddit

If you can't find the perfect wallpaper for your computer out of these thousands of constantly updated pictures, you're doing it wrong.