New Post: Category tree symbol

ok I see... there'll be a limit on the category name length and you're using it up with that HTML.

I would simply use the category image feature for this.

Add the icon as the category image in the category editor and then insert

[TAG:CATEGORYNAME] [TAG:IMAGE]

as the Tree Name Template in the category menu settings.

Use some CSS to adjust the vertical alignment.

The size of the image is set a little further down in the settings page - List Thumbnail Size.
Regards
Rob