To reduce the size of large images you might want to take only a part of the image. 

The following are several standard test images taken from image database at http://sipi.usc.edu/database/

aerial  boat  earth image

girl  house  MRI brain

The next image is dust-gas protuberances of Eagle Nebula from
rst.gsfc.nasa.gov/ Sect20/A2.html. One can find many astronomical images at that website.

Eagle nebula image from NASA website

The following group of  (larger in size) images is from Image Gallery at:

http://www.galex.caltech.edu/imagegallery.html

The Galaxy Evolution Explorer (GALEX), launched by a Pegasus rocket on April 28 2003, has been observing the sky using detectors sensitive to ultraviolet light.

Galex_crew_grayscale

Galaxy Evolution Explorer (GALEX) at http://www.galex.caltech.edu/imagegallery.html  GALEX  

GALEX  GALEX crew team


Hubble_Subaru.bmp