I got a bit carried away and have modified the workflow to better match my needs/wants.
Features I've added since 1.12:
Random file names (more difficult for people to guess your next screenshot). This will generate a random 4 character file name containing upper and lowercase a-Z and 1-9. A few ambiguous characters were dropped to avoid confusion when manually typing/relaying the url. (ie. lI0O) -- I believe this will be faster than the standard naming convention since it won't have to check if each numbered file before the current number exists. I haven't tested this but that's what appears to be happening. Option to skip a step when running "setups" again. Your current setting will remain untouched. Optimize image with ImageOptim (if it's not installed the the setting will be ignored) Save the capture in .jpeg format. This produces smaller files, but will disable to shadow on window captures.
All you need to do is re-run "setups", skip your existing settings and set the new ones.
Download 1.13
New in 1.14:
Added support for using jpegoptim and pngquant. These run in the background. Updated optimization descriptions since an optimized png can be smaller than the jpg verion.
Download 1.14
The latest updates to this script and my notes can be found here.
Enjoy.