TransTech few days ago released a transformation pack for N900. What it does, it only changes look and feel of N900. Here is a quota from the article.
Finally, after about 15 to 20 days of hardwork in my spare time (edit: and further 8 days of typing the guide), I have something really beautiful thing to give to my most loved community.Video and Apps that are Required after the break.
So this (Project) is called MaeMeeMo i.e. Its a mixture of Maemo5, Meego (Harmattan) and Nemo. As you all can see in the screenshots and the Intro Image (below), it has the goodness of Maemo5 (Homescreens), Meego (Harmattan) standby screen as lockscreen, and Nemo look and feel.
THIS is NOT an APP, its a transformation pack which requires some resources like themes, transitions, icons, depending apps and plugins. etc.
2.CSSU (Testing Flavor) [P.s. CSSU Stable not supported till further informed]
3.SSH (WinSCP Client or similar) (and knowledge of transferring files over ssh)
4.Backup-menu (or Backup-menu for Multiboot]
5.Know how to reflash [at rare cases]
Note: Download 2,3 and 4 and setup them from respective repositories.
Depending Applications, Plugins, Widgets Requirements:
1.Queen Becon Widgets
2.Theme Customizer (v63) [Extras Repository]
3.Custom Operator Name (Optional)
4.Advance Clock Plugin
5.QtLockscreen + QtLockscreen Configuration App
6.Harmattan Icon Pack for White themes
7.Harmattan Theme (White)
8.Catorise Plus with UI (optional)
9.Worldclock Mod by Ade (optional)
10.CSSU Features App
11.Desktop Activity Manager (optional recommended)
12.Nokia Pure Font
13.Gconf Editor (optional)
More info and Guide to do this you can find from here. MaeMeeMo Thread
Do it at your own risk if you are a noob then please stay away from it.