Have a look at Photobucket.com You can upload the photos there and then just copy and paste the link into NZFF. It also has the advantage that it means that you have a copy of your photo stored online too. Photobucket is free (at least the basic version).
There is no need for a 5mb photo if you are just going to view it online, most of the photos that you see here on NZFF have been uploaded to something like Photobucket, and will have been automatically resized to around 200-300kb and ajusted for on-screen viewing.
So do not worry about posting a large file, sit back and let one of the online photo storing sites such as Photobucket, do the work for you!!!
smooth landings.