Mrsolutions is absolutely right. Theme sponsorship is really hit or miss.. you might spend $100+ on a theme and it only gets used by a handful of people. Or you might spend the same amount and sometimes over 5,000 blogs are using the theme.
It is pretty easy to see which types of themes are popular - just go the themes.wordpress.net and look at the most downloaded themes. They typically have the same clean professional look - so only sponsor themes that have a similiar look and feel. With a little research you can identify the themes that will get downloaded and used by bloggers.
Yup .. I totally agree with your approach nichevalue. But sometimes its a lot easier said than done. I've sponsored my fair share of themes that were clean and awesome but haven't got the amount of links I expected. And believe me, I'm very familiar with themes.wordpress.net. Also note that number of times downloaded does not mean how many people use it though it has some correlation. I would suggest that themes with over 5,000 downloads are the themes that are good examples of what is successful. Also very important if the designer has a well trafficked and popular theme/Wordpress site. Headsetoptions is an example of a sponsored link seller that has a strong organic userbase because of their reputation as theme designers.
This idea can be picked only by programmers and designer. please give or create some easy idea for non-professional peoples like me. by the way this is really good idea and i am sure it really works.
You don't have to have any knowledge of programming or design - you just have to find people that will let you place sponsorship links in their themes. Yes the designers will charge you to place your sponsor link. But if you select the themes that you sponser carefully, you can end up with thousands of backlinks for a small one time investment.