Multiple custom login pages

[mweller]

I just purchased my first cP/WHM server and I'm in the process of migrating a bunch of accounts from an old Ensim box. I have 3 clients who require custom images on their wemail login pages. On Ensim this was simple... since everything is chroot'd for each domain all I had to do was replace the images in these domain's squirrelmail directories. Is there a way to do something similar with cP/WHM? I'm *thinking* that if I set these domains up as resellers and enable the option "Make the new reseller own their own account" then it would most likely be possible. Can anyone confirm this? Is there an easier way?

Thanks in advance

[mweller]

I just saw this in WHM -> Tweak Settings --> Display:

Default login theme [?]
The login theme to display for cPanel login. (If you are posting to /login/, you can include “login_theme” as a URI/form variable to overwrite this setting on a per case basis.)

I believe the the bold part is what I'm trying to do but I feel like a better explanation is needed. "Posting to /login/"? I don't get it.