I'm a domainer (and web developer, amongst other things) and would agree that these are worth, unfortunately, reg fee.
StockDesktopWallpaper.com seems to make sense, however 0 people search for that exact search phrase per month - meaning there's no easy way to monitize that domain straight away. In-fact, the domain would be a disadvantage for a website in the wallpaper niche since there'd be no on-page SEO benefit from the domain (since it wouldn't be worth targetting that keyword)
WallpaperSave.com doesn't make as much sense, but despite this 16 people search for that exact phrase per month ("wallpaper save"). However nonetheless, this is too low to consider making a website around (you'd need to aim for 2,000+ exact monthly searches, IMO).
But as mentioned above, a domain is worth as much as a buyer is willing to pay for it. Here's hoping you find one
As a general tip, when looking for a domain to register (especially a keyword one like this), remember things like:
1) Does the keyword make sense (Would people naturally search for "wallpaper save", etc)
2) Does the keyword get any real monthly searches (check via Google Keywords Tool)
3) Does the keyword have low competition (Search the exact keyword via Google, and check-out the first page competition)
If the keyword makes sense, gets a fair number of monthly searches, and has no real competition, it could be worth going after and developing.
But if not, then you have to ask yourself where its value comes from if it's not worth developing. In 99% of cases, a keyword domain which doesn't fulfil the above 3 criteria usually isn't worth registering.