Is there any way to replace VS2012 solution explorer\'s icons with VS2010 ones? At least \'folder\' icon :(
Short Answer: Hack the old icons into 2012.
Visual Studio Icon Patcher - http://vsip.codeplex.com
Long Answer: Doing this with a plugin, for now, is out of the question. I've been unable to find any built-in way to achieve this and the switch to WPF makes it even harder to hack around.
This app simply extracts the image resources from the unmanaged DLLs in Visual Studio 2010 and injects them into the DLLs for Visual Studio 2012. The managed resources are a lot more complex and haven't been added in yet, though I have gotten some to work.
The initial release didn't work well with themes that had a dark Tree View background color due to how the icon colors are inverted when a dark background color is detected. This is made even worse in the newest release since menu & toolbar icons are included now. I'm running this with the Blue Theme and it looks fine.
One way to hack around the icon inversion is to edit all the extracted images to add a single cyan pixel in the top right corner of each icon in the image map. This will exclude them from the inversion process. I haven't tried this though because I ran into issues early on when manipulating the images where they wouldn't display right. You could try it but it'll be fairly manual and time consuming and may not even work.