How about, for additional effect, money flies everywhere when the Scout wearing this is gibbed.

it looks so 2012, come back in 17 years

Rather boring, and the blank white texture doesn't really fit the Scout; only the Medic has large white parts on his body model for easy class recognition.

And there already is a duffelbag for the Scout's back, with dollar bills that come fluttering out: the Dillinger's Duffel, which has been in the game since summer 2012
https://wiki.teamfortress.com/wiki/Dillinger%27s_Duffel

I like the concept, but I don't really like the money's texture. Namely, I think the Scout's picture should be green (to match the bill's colours) and the font should be something other than Comic Sans.
Other than that, I like it!