It depends on how much visitors you get on your website. You can add advertising to your website or partner with ad networks like google adsense. You can earn up to $8 per 1000 visitors on your website with google adsense. But keep going. You can later implement more things and maybe earn up to $20 per 1000 visitors.
There are some wallpapers site listed on DP Website Market Place, some of them imported there AdSense earning data, look at & check there website how they have placed ads on there site. You will able to get the answer of your question.
The thing is about these types of web sites is 100% of your traffic is looking for FREE wallpaper to download. There's a very very slim chance they are going to click on any ads on your site unless those ads advertise FREE wallpaper. If so, you probably will find the payout to be quite low....as it's free virtual stuff... Low CTR + Low CPC = Low Return. Sorry I don't see this making anything more than a few bucks off from accidental clicks.
Did you search first? https://www.google.co.nz/search?q=site:forums.digitalpoint.com+earn+wallpaper+site
the only way to make money out of a wallpaper site is to get the people actually interested in your SITE rather than the content, why not make some wallpapers and get them showcased on some design blogs? ( free backlinks and traffic ) the momentum keeps on building up and you might actually have something on your hands
First, do people still make wallpaper sites? I thought they were hot back in the late 90's. Second, I don't believe for a second that anyone can make money from a wallpaper site.
A wallpaper site is just that... a site for wallpaper... The only thing they are interested in is your content.. They don't care about you blogging about your designs or anything else other than wallpaper which is what they are looking for.