I use Gimp for picture enhancing. As Jim said, scale them down. 900 width works for me but they can be a little wider.
I sometimes use Notepad to do the writings. That way I don't need to do it at one go but can store them as plain text and copy&paste them later.
To spice up the posts with maps look here
. There are other sites as that one but this I like best for the Eastern theater.
Fantastic photos can be found here
. Although from the Union perspective mostly there are many pearls like this
some of the same photos and additional ones can be found.