LOZ, excellent idea! Personally I'd probably use an IS vest, but I'm not religious about it.
On my EOS gear the first thing I do is remove the stock strap (the one with "EOS DIGITAL" [pronounced "STEAL ME"] stamped on it) and replace it with Op/Tech straps (for use with one of the logo-less shoulder straps I share amongst my cameras).
My Canon lens caps are replaced by Tamron ones with the silver logo sanded back (but this replacement is more for functional reasons than aesthetic ones).
My vest (a Domke: my wife says it's pronounced "Dorky"
) has a subtle Nature Photographers Network badge on a pocket, but that's about as far as I go.
Of course, when I'm carrying my big gear there's little doubt that it's worth some serious money, so who am I kidding?...
Canon gave me an "EOS" hat (complete with subtle red ring around the brim) but I'm not all that keen on being a billboard. It IS a neutral grey colour though...