SorryPage with iFiles on 11.3 HF8

So then just to level set, did you remove the initial if { [HTTP::uri] eq "/sp" } evaluation? What does the log statement report? Do you see the request for the /logo URI? How about some additional logging just to make sure:

when HTTP_REQUEST {  
    log local0. "HTTP_REQ: Requested Hostname: [HTTP::host] URI: [HTTP::uri]"
    switch [HTTP::uri] {
        "/sp" {
            log local0. "catch /sp"
            HTTP::respond 200 content [ifile get "index"] "Content-Type" "text/html"
        }
        "/logo" {
            log local0. "catch /logo"
            HTTP::respond 200 content [ifile get "logo"] "Content-Type" "image/png"
        }
        "/background" {
            log local0. "/catch background"
            HTTP::respond 200 content [ifile get "background"] "Content-Type" "image/jpeg"
        }
    }
}