The express version can compile resources but it cannot edit them. I have tried with dialog box resources and menus, not with bitmaps, but I think bitmaps should work too. However, the "add - resource" menu item is greyed out and the IDE will not create the header automatically. So you have to somehow create your resource file (with external resource editor, I don't think you can write a bitmap resource by hand as I first did with dialog boxes...), then add the resource file as "existing item" to your project. Also create manually the header file (or maybe the resource editor will also save the header for you). Then it should compile. For editor I use this one:
http://www.resedit.net/ and save the result as "rc" file. The "res" file is generated by the compiler.
EDIT: I don't know if there is any limitation on the size of the bitmap resource you can load or what you can edit with this editor. You need to test if it's suitable for a whole heightmap.