What is the 'proper' title for someone who is a graphic designer, music composer, photographer and a videographer all together.

Thirding Multimedia Producer - although I might title it "Multimedia Producer / Creator", then spell out the characteristics if there's room.

Dilettante

Content Production

Executive pixel pusher.

Multimedia Deigner, Manager, Specialist, or maybe even Master

It probably depends on what industry we're talking about, and the level of seniority of the person in question, but Creative Director sounds about right. Or Associate Creative Director for someone who's less senior. Or Executive Creative Director for someone who's more senior. This has the added advantage of being an actual title used in actual business, and doesn't sound made-up the way some of the suggestions above do.

Oh, seconding "Creative Specialist", good one joshrholloway :)

Multimedia Producer or Multimedia Designer, depending on the image you want to portray.

I've said Multimedia Artist. Or if you work with mostly electronic artistry, a Digital Artist. I kinda like Art Director more than Multimedia Producer though. Multimedia Director? God, choosing a title is an art in itself...