2 - dpi doesn't mean squat until you actually go to print an image on paper.

An 8261x5653 pixel image is the exact same image whether it's 10 dpi, 72 dpi, or 600 dpi.

If you go to where you can find the "Earth Textures" they are ginormous as well (21600x10800 - no kidding!) - enjoy! Otherwise, if it's posted on the web I usually find a limit to their size is under 2,000px - stock sites will have larger files.

-Lew