Argh!!
A friend of mine who admins the boards has just written this same hack! We've had the same thing in beta for the past 3 months, at least
We have a secondary server donated by orange.net which we save attachments in. At the moment we have database connections, and attachments are brought through using the same attachment.php file - I did intend on having a remote attachment.php but thats step 2... Just got it up and running tonight, as we've had mySQL problems!
I can't believe it! hehe...