Quoting Ronan Zeegers <inkscape@...1494...>:
It's important if we want nice and crisp icons in the menu and for the toolbars at the same time! I'm working on the problem for a new set of icons but it can be good if a real coder can take a look at it... 2 icons instead of 1 for each element should do trick --> "draw_calligraphic" whould become "draw_calligraphic_16x16" and "draw_calligraphic_22x22". 2 differents icons for 2 differents rendering res...
Actually that's breaking the intent of SVG icons to begin with.
Once 0.45 is out the door, I can get into adding multiImage support for Inkscape. Then at the very least our own icons will be able to have multiple versions without falling to that name hack.
I've also submit a bug report about this different size icons problem for the toolbars between system (windows vs linux): n° [1568475] Please, take a look and tell me what do you think.
OK. I've reviewed that and... "not a bug"
The effects you are seeing are exactly as intended. Inkscape is generating icons the size requested by the current theme. Use a different theme, get a different size. "Large Print" is one theme that is very good for exercising this.