Add more icons

[Nudin]

There are not enough icons and the choice of icons matches only some peoples needs. There are several tickets proposing to allow usage of arbitrary icons via unicode/etc but it seems they won't be implemented, at least not in short term.
So please add more icons.

We could use this ticket to collect icons-topics:

• audio (A speaker or a music note)
• video (A filmroll or playbutton)
• pictures (A camera)
• A question mark
• A book
• a gear
• Social media (connected graph)
• mail symbol
• a clock

[vibhas77]

Please see #843 and #984

[grahamperrin]

Mozilla bug 1533542 - Tab containers: Need more icons to choose from

[dreirund]

I would then make it general from the beginning -- let users select an arbitrary image (PNG, GIF, with appropriate size) from their harddisk or unicode character.

[santo998]

Will you add more icons to the containers?
i.e.: a government icon (building), an education icon (graduated student).

[dannycolin]

duplicate of #2368