marketpress - adding fields to posts using custom fields template plugin

ok I nearly have marketpress set up to work with my site, all good s far.

I would like to bypass the wordpress image uploading method (both featured image and images in posts)

I have achieved this so far by adding the custom fields template plugin and adding a field to the product creation page which uploads 3 photos (screenshot added here)

The problem is the plugin doesnt work across the other sites in the network ...

So is there another, simpler, plugin you know about that I could use to do the same job? Or does anyone know why custom fields template doesnt show the template on networked sites?

I think wordpress allows me to add custom fields, but I would have no idea what code to put inside to upload the images. It just needs to function in the same way as the button which allows me to add an attachment to this post.