My 'custom command' for Shutter is as follows:
/usr/bin/shutter -s -e -o 'Screens/%name-%M-%D-%Y_k0nsl.png'
I append "k0nsl" at the end due to habit and because when I upload it to a service such as 0x0f.su it will be easier for me to keep tabs on things.
What's more, the compression is set to zero in Shutter and after a screenshot has been taken then OptiPNG is executed for post-processing — with a compression level of only "2"; this is optimal for my usage scenario, but yours will likely differ from mine.
That is all.
 Shutter is a *nix application that allows you to take screenshots, edit them, apply various effects, upload them online and more.
Other applications and/or tools used: pngquant, pngnq and pngcrush.