A blog with super heavy traffic will create super heavy earnings,undoubtedly.One of the most searched keyword in search engines is 'FREE'.People want to download free wallpapers for PC and mobile phone, free vectors, free textures, free ringtones and free themes for their mobile phones, free horoscope,free games, free downloadable songs and want to watch free movies.
Now if you are able to provide any of these in your blog, that too copyright free,then you hit the jackpot for sure.
If you know photoshop,or any other advanced photo editing software,create some standard resolution wallpapers.Let it be colorful.It is really easy,use your creativity and make the most beautiful and unique wallpapers.Once you have done,you can upload it directly to blogger or you can upload it in any photo hosting website and post the links in your blog.
The word 'Free' is a magical word.Even the richest guy will run behind 'Free Offers'.So once you have lots of quality content,you can use text-based ads like google adsense here.Google adsense works best at wallpaper sites/blogs.People clicks on the text ads without thinking and the cash register rings every second.
Use google adsense link units or text only buttons between your posts.Make them the same color of the downloadable link in your blog.