L: Let's liven this place up
It's still the AtoZChallenge, and the Letter is L.
Liven: verb (used with object)
to put life into; rouse; enliven; cheer (often followed by up):
What can we do to liven up the party?
verb (used without object)
to become more lively; brighten (usually followed by up):
If this party doesn't liven up soon, let's leave.