Astronomy Picture of the Day has some modified pictures, like this cool one.
APOD: 2013 February 19 – Mercury on the Horizon
When has image manipulation added to our understanding, and when has it gone too far?
The Ethics of Digital Manipulation
More about Mercury
See Mercury at Sunset – NASA Science
Not manipulated
APOD: 2005 September 13 – A Quadruple Sky Over Great Salt Lake
APOD: 2002 May 10 – Trailing Planets
APOD: 2012 May 20 – A Partial Eclipse Over Manila Bay