Having upgraded from 11.4 I now find I am restricted to just 4 themes. I installed 4 others through package manager but they are not offered when I right click the screen.
Are there ways to use these other themes.
Thanks in advance.
I take it you’re using the Gnome shell rather than Unity ?
If so, you need to install/use the Gnome Tweak tool to enable themes (and any other shell extensions) … see here:
http://www.techdrivein.com/2011/10/how-to-install-and-manage-gnome-shell.html
Have fun with your new Gnome 3 (shell) learning curve … we all had to go through it 6 months ago … most things ARE achievable in Gnome 3, but they are done differently to Gnome 2.x 
There are some topics on here somewhere about tweaking Gnome 3 … but if you get stuck, or can’t find them, gimme a shout
Thanks again but you would think these things would be installed as standard.
Will now know what to look out for how dose 12.4 comparer with 11.10 in the classic desk top stakes?
AFAIK it’s exactly the same.
If you want a Gnome2 style desktop, there are 2 projects that may interest you
CINNAMON … Linux Mints attempt to add custom extensions to to Gnome3 to make it as much like Gnome 2 as possible.
MATE … a fork of the Gnome2 desktop environment, which allows you to still use the Gnome2 desktop on new versions of Mint/Ubuntu
Personally I’d go for Cinnamon, IMHO MATE will die (and should do so), Gnome2 is dead and aint coming back.
Both Cinnamon and MATE are available now through PPA’s for Ubuntu … or come pre-installed on Linux Mint.
I will try it when I upgrade my mint 10 system…
Thanks.