Base Properties Question

Hi,

Is there a way, without the use of "SiteRoot" to force
sub-portals/folders of a Plone site to use it's own 'base_properties'?

For example, I want to have a root 'plonesite'.  Underneath, I have a
folder called 'foo' – which will be a portal, with different colors
for the buttons and a different logo/banner.  I can't use the
'SiteRoot' as I don't want the URLs to be anchored to that portal.
I'm sure there is a simple way to invoke this.  We also would like to
dynamically reference values of our banner image's "alt" and "title"
properties from the base_properties.  Any ideas?

Thanks in advance!

Rashid Chowdhury