[ewebartist]

I think I figured out a quick fix.

In the following section of /admin/main/membership_signup.tpl

{foreach from=$membership_levels item=v}
<option value="{$v.membershipid}"{if $userinfo.pending_membershipid eq $v.membershipid} selected="selected"{/if}>{$v.membership}</option>
{/foreach}

add the following if statement as follows:

{foreach from=$membership_levels item=v}
{if $v.membershipid eq "1" OR $v.membershipid eq "2"}
<option value="{$v.membershipid}"{if $userinfo.pending_membershipid eq $v.membershipid} selected="selected"{/if}>{$v.membership}</option>
{/if}
{/foreach}

where the membershipid is equivalent to the ID of the membership level you would like to display in the drop-down (Hint: try experimenting with 1, 2, etc until you ahieve your desired options set)

With this done, you will be able to create as many membership levels on the admin side, and designate a user to a particular membership level after they register without them having access to it on the registration page. Hope this helps!