Two major problems that i am sure you are aware of :) are...

#1.Hard to find AV/Automation icons.

#2.When you do find some its not a whole set and the others don't match.

Because of this i would suggest you take a look at the commercially available icon sets from industry GUI pros. They will have what you need because the set is specifically target towards us.

[Link: ntdesignsonline.com]

[Link: blackmancustoms.com]

[Link: customcodecrafters.com]

[Link: guifx.com]

Free stuff::::

This is a list of free icon sets i have found on the web. All have transparent png versions so you can scale them and use them however you want.

[Link: guijaboard.com]

This is a quick-n-dirty set of icons i put together a while back. Its pretty good for personal use but since most of the graphics dont belong to me (or you) i would suggest keeping them off clients remotes and touchpanels.
[Link: guijaboard.com]