Growl is always one of the first things I install on every new Mac. It’s a fantastic notifications system that displays small popups to let you know when all sorts of things happen. You can get notified when new mail arrives, when a song starts in iTunes, when downloads are finished — literally hundreds of applications are compatible with it.

It seems Growl is having a few teething problems in Lion, one of which is that lots of themes need to be rewritten. Luckily, my all-time favourite theme, Mono, has just been updated to be Lion compatible. Check out the beautiful theme in the screenshot below.

While checking out which themes are Lion compatible, I also came across a new theme called Black Glass that might give Mono a run for its money. You can see it in the screenshot below, but you really have to go view the preview to appreciate its slick animations.

One additional problem with Growl in Lion that you might encounter is that sometimes the newly installed themes refuse to appear. There’s an easy fix — go to Activity Monitor (located in Applications/Utilities) and find GrowlHelperApp in the list. Select it and click Quit Process, then stop and restart Growl from its preference pane in System Preferences. Your new themes should now be working perfectly.

[Update: Christian has posted a link in the comments to his own customised Lion-compatible version of the Smokestack theme.]