images is not loading correctly

You can simply tweak this part, so it matches your requirement.

when HTTP_REQUEST {
if { [string tolower [HTTP::uri]] starts_with "/gamification" } {
HTTP::uri [string map -nocase {"/gamification/" "/"} [HTTP::uri]]
}
}

Explanation:

set newuri [string map -nocase {"/gamification" ""} $uri]

Will give you "_uploads/header.jpg"

But being specific like below,

set newuri [string map -nocase {"/gamification/" "/"} $uri]

Will give you "/gamification_uploads/header.jpg"

Hope it explains.