Hi Bjorn,
My advice is no you don't want to do that. If you really want to show the menu there is a way to do it but I recommend against it.
<add key="HideMenusOnRegisterPage" value="false" />
The registration page (and the login page) is specifically designed not to be a content page and best practices are to not have any distractions on the registration form. This reduces conversion rates for registration among other things.
Furthermore if you are using SSL as you should on a registration form then having content in a feed will more than likely cause browser warnings about the unsecure content on the secure page because any images with src=http:// instead of https:// will cause browser warnings and this will scare off the user from registering.
Making a page secure requires having tight control over what is on the page so both from a security perspective and from the perspective of wanting to increase registration rates we don't want extra content on the page, we want to keep the user focused on the task at hand with no distractions and extra content or links that encourage the user to click away from the registration page are not a good idea. If the user clicked the link to your registration page that means they want to register, we don't want to give them distractions to change their mind.
Best,
Joe