Mouse cursor theme change
I'll describe my experience with mouse cursor changing in Gnome 3.2.1. I had big problems with it and I discovered, during my finding a solution in past, that many others have that problem too.
I have done the change successfully with the Large Mouse Cursors downloaded from gnomelook.org.
Now I'll describe the advancement how to change the mouse cursors.
Advancement for first use of new cursor theme:
1) Put the directory named as the name of cursors is into directory /usr/share/icons. The directory of cursors can be obtained by for example downloading and potential unpacking.
2) Log out and in, press Alt+F2, write "gnome-tweak-tool" and press Enter. The Gnome tweak tool window will display. In leftside column click on Theme and on right half of window unpack the menu "Cursor theme". That menu now should contain also the name of your new cursors from step 1).
3) In menu Cursor theme in Gnome tweak tool should be set the cursor theme which is used till now. First, by clicking on Cursor theme menu, choose some cursor theme different from that, which is used till now, and simultaneously different from that your new theme. Second, again by clicking on Cursor theme menu, choose your new cursor theme. Press Alt+F4 to close Gnome tweak tool window.
4) Open any program, for example Mozilla, Gedit... Now, new cursor should become to be used.
Advancement for another next use of new curdor theme.
Proglem is, that if you log out, restart or shut down and than restart, new cursor theme will be used only till you will log in. Therefore you have to do steps 3) and 4) after every logging in. Still used cursor theme displayed in corresponding menu in Gnome tweak tool will though be your new cursor theme, but it will not be used except if your mouse will show into for example Mozilla window. Therefore it's necessary logging in to change it to another mouse cursor theme and back, as described in step 3). After that, for activating new cursor theme, the step 4) is very necessary.