Merging multiple iconsets into one? And weapon set usage.

I have a couple iconsets from different artists that I want to combine into one because I have multiple classes, etc that use icons from multiple sets. And since I realized that you can only have one iconset in your system folder at a time (and if you have multiple, something something hierarchy...), I'm at a loss...or I'm just tired...

I have GIMP but havent used it in almost a bajillion years, if that matters.
of course all credits will be given to respective artists in the endgame.

Oh and before I forget, how does one use the animated weapon sets (like the ones from Avy and hiddenone?)

 

Simple IrfanView can do it, open it and in menu

Image -> Create Panorama Image and in window wich appears select Vertical option and load those iconsets and click Create Image

 

you can merge all iconset.
Just keep 1 thing is mind that the MAX Width = 512 and not wider than that.
the Height doesn't matter so far I know.

What do you mean animated weapon sets?
as stepping or in battle?
Maybe a link to the set would be helpfull?