You could defined a different port in your img tags. Then you can start
thttpd to bind to that port. You shouldn't have a problem binding to ports
higher that 1024(?) I think. Unless they have done something to prevent
this which is doubtful.
Example:
img
I have a high traffic website (looks like 200 GB output per month,
something around 10-20 hits per day) hosted on a commercial
service. The service does not limit my bandwidth usage, but they limit the
number of concurrent Apache process that I can have to 41. This causes the
server