[Lynne]

I would add a plugin, or modify the template, to add that background css just for that forum - example for if in headinclude template:

<if condition="$forumid == 'xx'">
<style type="text/css">
<!--
.the_class_you_want_to_change{
    background: #d9d9c2;
}
-->
</style>
</if>

As for the new thread button - it's in the SHOWTHREAD template in two places. Find it and remove it.

And posting limit - take a look in the mods forums for one.