Check your firewall's log. Look to see which traffic has been blocked. (ZoneAlarm, in particular, has a nasty habit of blocking pictures from sites like photofile.ru). If you spot that traffic has been blocked from the sites which you want to get pictures from, you'll have to do whatever is required to change your firewall's settings).
Another cause of missing pictures is server time-outs. This can occur when the main structure of the web page is loaded from one server but the pictures come from a secondary server. At times of peak traffic, the secondary server can't provide the images before the system times out. Clicking 'refresh' can sometimes resolve this problem.
One last thing to check is your browser settings. Some browsers offer an option to block pictures which do not come from the same site as the main part ofthe web page. (OE6 doesn't seem to have this feature but Firefox does). Check that this facility is disabled. (In Firefox, go to Tools > Options > Web Features. Ensure that there's no tick in the box 'for the originating web site only').
Chris