MZ-Tools Articles Series (Updated): HOWTO: Creating custom pictures for Visual Studio .NET add-ins commands, buttons and toolwindows.
Recently I have migrated the next version of MZ-Tools for Visual Studio .NET that I am working on from COM-based add-in to XML-based add-in (giving up Visual Studio .NET 2002/2003 support). I tried to do it many months ago but I gave up because moving to XML-based add-in meant also moving from native resource DLL to managed resource DLL, and I didn't want to do that at that time, I just wanted to get rid of COM. But tired of the two bugs in the Visual Studio 2005/2008 Add-In Managers with COM-addins (the former one only fixed in VS 2008 and the latter one reopened and again under investigation after strong discussion with Microsoft), and tired of the problems of COM and transparent bitmaps, etc. finally I have moved to a managed satellite DLL.
AFAIK, the only official documentation from Microsoft to build a managed satellite dll for a XML add-in is the following gem in MSDN, that involves using command-line tools such as resgen.exe (Resource File Generator) or al.exe (Assembly Linker) and Windows tools such as Notepad:
How to: Display a Custom Icon on the Add-in Button
How they can sleep well with that is beyond me ;-). I am currently trying to convince the Program Manager in charge of this to support resources in the own dll of the add-in for VS 2010 so maybe in 2014 your add-in targeting VS 2010, VS 2012 and VS 2014 can get rid of the resource dll...
Of course there is a much better way to create a resource dll that doesn't involve command-line tools, that is, a class library project in the same solution of the add-in that provides the resources. I have updated the following article to cover this scenario:
HOWTO: Creating custom pictures for Visual Studio .NET add-ins commands, buttons and toolwindows.
I have updated also the section about toolwindow bitmaps to provide better information. I have not included yet information about VS 2010 but you have these other posts:
Solved: transparent bitmaps in add-in toolwindows of VS 2010 (Beta 1)
Solved: transparent bitmaps in add-in commands of VS 2010 (Beta 1)
I will update the article when the current two bugs under investigation are solved in some way or another and VS 2010 gets release candidate status.