Maybe it's from the Nokia Research lab's repository?

To be honest, I have no idea. The maintainer is "Michael Kostrzewa@nokia.com".
It's in a category called "Themes".
Details in the app manager calls the packages:

hildon-theme-chacher 0.2.0-1 (needed by the two themes below)
hildon-theme-plankton 3.1.0-1 (nice blue theme)
hildon-theme-sketchy 3.1.4-1 (bizarre "sketch" theme looks like everything was done in pencil)

I'm on the latest and greatest skype-enabled firmware (v4) running the micro-b beta and the SIP beta and both themes work just fine.
Take note that they both use the default font and icon sizes.

Here's my current sources.list file:

#maemo:name Nokia Catalogue
#maemo:essential
deb http://catalogue.tableteer.nokia.com/certified/ bora user
#maemo:name Nokia Catalogue (3rd party software)
deb http://catalogue.tableteer.nokia.com/non-certified/ bora user
#maemo:name OSSO RTCom Beta
deb http://repository.maemo.org/rtcomm bora free
#maemo:name bora-extras
#deb http://repository.maemo.org/extras bora free non-free
#maemo:name MUlliNER.ORG Maemo Software (Maemo 3.x)
deb http://www.mulliner.org/nokia770/repository/ bora free
#maemo:name Eko
#deb http://eko.one.pl/maemo/ bora user
#maemo:name Maemo Repository
#deb http://repository.maemo.org bora free non-free
#maemo:name Maemo Rep Extras
deb http://repository.maemo.org/extras/ bora free non-free
#maemo:name Wesnoth mirror
#deb http://blackax.net/Pub/wesnoth/ bora user
#maemo:name Nokia Research
deb http://repository.nrcc.noklab.com/ bora extras
#maemo:name Tortoise