Attached please find some potential logos. There are two general approaches: one sort of implies a unifying approach around a central "Lucene" theme, and the other is a standalone sort. And now, since LCF has become ACF, and ACF has become ManifoldCF, we need a whole new set.
"Lucene" themed logos
Classic with pictogram:
Standalone logos
These would be corresponding Lucene/LCF logos:
Here's another central-themed LCF logo, based around a bridge:
Another modest option:
New Apache-themed logos
(There are two other .svg files attached, but I don't have .png's for them yet.)
New ManifoldCF logo
Same logo with the TM, as required by Apache
The C and F make up a socket. The Apache feather make up the cord 
