With such a message open, showing the X's, look in the header for a link
reading "Download Pictures". Entourage does not download graphics when they
are linked to separately from a message. This is done to protect you against
spammers and phishing, as opening an image on a remote site can transmit
info about to the the site. You can choose which messages you want to
download the pictures for.
Actually, that security feature only exists in Entourage 2004. In Entourage
X, go to Entourage > Mail & News Preferences, and click the "Read" tab.
Make sure the options to "Display complex HTML in messages" and to "Allow
network access" are checked. If those are turned on, you're connected to
the internet, and Entourage is set to work online, the pictures should
appear.
I fear there's not much you can do about the speed; complex HTML messages
always seem to take longer to render in Entourage.