I am trying to store and display a map for an RTS game as a texture2d, but the map is too big, and I get the error "XNA Framework HiDef profile supports a maximum Texture2D size of 4096". The reason I wanted the entire map in one texture was so I could take advantage of the source/destination rectnagle draw method that spriteBatch has for use in the games camera. If this isn't obviously a bad idea, how can I store and display large images?
You can't get around the texture size limit in XNA. It's quite reasonable to use multiple textures and draw them in different places. It is only a small amount of extra logic to handle the borders.
Don't forget that a 4096 by 4096 texture is already a whopping 64MB of texture memory, uncompressed (and at least 10MB if DXT compressed).
If you're concerned about performance - don't be. The "source rectangle" parameter enables texture atlasing - this is not what you're doing here, though.
Furthermore, it is usually best to implement a game camera by passing a translation Matrix to SpriteBatch.Begin, and then Drawing everything (background included) at fixed coordinates. You don't even need to specify a source rectangle for the background - the viewport will simply clip it.
If you wish to import textures that are larger than 4096 square, you could create a content pipeline extension to cut those large textures up into smaller ones. Or, if you only have a handful of fixed maps, it is easier just to separate them in your image editor.