If you're on a PC, I strongly recommend using Irfanview. It is free for non-commercial use, and it gives you a lot of tools to manipulate images but it is very easy to use.
I take most of my photos at high resolution (6000 x 4000) and use Irfanview to reduce them to 600 x 400 before uploading them. Sometimes I'll crop out stuff on the sides that isn't needed, like the edge of the pan.
It has a batch mode for processing large groups of photos, but I usually do one or two at a time, so I don't use that mode a lot. You can manipulate all the way down to the pixel level.
I have something called a ShotBox, which is a portable small photo studio / light box with several photo backgrounds (a Christmas present from my son, who was one of the kickstarter participants for it), but I also went to the craft store and bought a 20x30 sheet of foam board that I use as a background for larger things.
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