display svg icons and thumbnails

I've just done an install on a new machine and have completely forgotten how to
enable this - unfortunately it's one of the few things I didn't put in my
notes :(

Anyone know how to do it?

-- 
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.

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