After working with the Mac4Lin package for a couple of days, I have to say I'm very impressed. I'd be happy to help with future development (documentation maybe, or whatever needs doing) if there's a need. In the mean time, I have a few notes, observations, and questions to pass on.
I started out using the Emerald theme, but ended up going back to Metacity, for one main reason - the titlebar font. Neither the font choice nor the font smoothing settings from Gnome Appearance Preferences are used by the Emerald theme. The font can be changed in the Emerald theme, using the Emerald Theme Manager, but since the smoothing settings aren't used, it still ends up looking pretty bad next to the fonts used in other areas. Since there's no difference in the look either way (at least none that I can see), I prefer to stick with Metacity.
I didn't find anything in the existing documentation specifically about configuring the panel, but it appears from the screen shots that the Notification Area was eliminated. Individual applets, like the Network Monitor, can be added, but some apps don't behave normally if the Notification Area isn't there. Pidgin, for example, shuts down when its window is closed rather than running in the background. Other apps and applets that have problems include Network Manager, the Update Manager (mintUpdate), and Amarok. If monochrome icons could be added for those apps, the Notification Area could be left in without disrupting the look.
I tried putting the icon theme in /usr/share/icons, but it appeared that they weren't accessible from there for some reason. I had to install them from Appearance Preferences, which places them in the user's home directory, before they were usable; although I may well be missing something. It would be nice to put all the theme, icon, and cursor files into usr/share to make them accessible from all user accounts; any idea what I might have been doing wrong? I did set normal owner, group, and permissions for all files after copying, BTW.
I couldn't get the cursor theme to work completely until I uninstalled Emerald. It was strange - I would get a black cursor, per the new theme, in certain windows, but in other windows or on the desktop, it would turn white (the original theme). Once I uninstalled Emerald, it worked fine. There might be something else at work here, but that's the only correlation I could come up with.
That's about it, for now, other than it would be great to bundle it all into deb/rpm files for easy installation.