Do you want to create a patterned background, or is something like this what you're trying to do? You're wording isn't clear.

Sorry, but I don't have enough rep to post this as a comment.

[Edit] I never explained what I did because OP never answered my question. I still don't know what she actually wanted to do.

Anyway. Downloaded the two images. Placed the map on one layer and the sunrise image on a layer above it, centering it roughly over Tibet just because. Selected the blue and gray areas on the sunrise layer, then inverted the selection. Created a new layer and filled the selection with black. Deleted (or made invisible) the sunrise layer. Added some text. Flattened. That's one way.

Another would be to add a mask to the sunrise layer, select the blue and gray areas and then fill the selection with black in the mask to block out the sunrise. Go back to the image proper and delete the white, then select the entire layer and fill with black. Create type layer. Flatten.

A third would be to create a layer between the map and the sunrise, fill it with black and add a mask. Go up to the sunrise layer, select the blue and gray areas, then back to the mask and fill the selection with black. Delete (or make invisible) the sunrise layer. Create type layer. Flatten.

Have I beaten this to death yet? This was almost 6 months ago. I don't remember exactly what I did. :-/