Greetings,
Most pics I download I alter in some way. Some I crop to rid the pic of a logo or watermark. Some I brighten or darken or enhance the colors. Some folks have PhotoShop or another paid-for program to enhance/alter/whatever their pics.
For several years I have used PhotoFiltre, the free version. After trying several free programs I settled on PhotoFiltre due to its basic abilities that work very well for my needs along with ease of use and a gentle learning curve.
One aspect I like is the ability to copy a portion of the pic then paste that portion. I can then move the pasted portion around to cover a logo or watermark.
With a little practice and trying the many aspects of the program you can quickly enhance downloaded pics.
I particularly lke the "sharpen" control. Often, I can alter a fuzzy low-resolution pic, such as the type seen with some of the Met-Art freebie pics, and improve it so as to make the pic much more enjoyable to use.
I do not know how much longer the free program will be available so, if interested, I recommend grabbing it.
I haven't tried every free image altering program out there but of the ones use I like this one best.
http://photofiltre.free.fr/frames_en.htm