Icons smaller than 24px

[Nate_the_Ace]

I just want to start off by stating that the new Humanity theme is awesome. I only have one complaint, the volume icon in the upper panel changes from its sleek look to some cartoon-ish mess when the panel is under 24px wide. My preferrence would be to have that modern gray icon go all the way down to the minimum 19px. I love having as much workspace as possible on my desktop, (I even set the autohide width to 1px) but I definitely don't like the look of that colored icon.

How could I change it myself? How would one resize the icon files in GIMP to fit my requirements?

Attached a screen grab, so you could share in my ocular disdain.

No step by steps needed here, just ideas.

Thanks in advanced-
Nate