Rewrite help!!!

ltm v 12.1.2

I need to rewrite a url from a shortname to the real backend https://wfeserver.wfe.co.uk/portal so th euser never sees the real url and also only has to type a shortname - this is easy enough using uri translation in a rewrite profile. However it appears that are images on the real url https://wfeserver.wfe.co.uk/portal to form the page which are called from another server location; so when the rewrite profile is used it does not see them and they are not displayed.

How can achieve what I need? is there another way? any guidance/help would be appreciated