I would dig around and see if someone has worked with conditionals and ranks, I wouldn't doubt it's been done somwhere. As an alternative you could use promotions and usergrops to accomplish this. For example, say you want the user to have image1.gif at 500 posts and an
additional image2.gif at 1000 you could do it by setting up groups.
Setup a group for image1.gif (add as many groups as you want)
Setup a promotion for the user to be added to this group with a certain post count.
In your postbit (and optionally memberinfo) you would add something like this for a condition: (I put mine under the avatar)
Code:
<if condition="is_member_of($post, 48)"> <a href="vb/subscriptions.php"><img src="/vb/images/ranks/plat.gif" alt="Platinum Member" border="0" /></a>
</if>
$post
48 being the group number
Optionally, you can add as many as you want this way