SQL Server Management Studio 2012 - horrible blue background
Are you talking about the below appearance?



If that's the case, then I don't think that blue background is able to be changed.  I'm not sure why that'd be such a hang-up, as if you're staring at that background in SSMS, then you're probably not really doing anything.  Like Martin said above, the query window or other placeholders in that area will cover that completely.

When you have a query window open, it should look similar to the below screenshot:



As you can notice, you don't really see that blue background at all.  99% of the time (at least for me when I'm in SSMS), this will be the visual representation of SSMS.