Very welcome to the forums, Scanman!
Hi. I have few questions.
1. How to give to user read only rights to all except his home folder?
I take this to mean that you don't want your users to be able to write
to anything outside their home folders. If so, that is the default.
If you also mean that you don't want them to be able to execute
apps outside of their home folder, that is more problematic. It would be easy to set up, but they wouldn't be able to run any globally installed applications; they wouldn't really be running PCLinuxOS anymore. If they'd only be able to run programs installed in their home directory, they'd be running a very crippled setup without most of the things normally installed with Synaptic.
But if you mean that you don't want them to have access
to folders outside their home, i.e. look at what's in them, thats easily fixed. (E.g. traditionally nobody but root has been able to access the /root folder. In PCLinuxOS 2010 anybody can do it, but that's probably an oversight, and as I said, not hard to fix.)
So if you could be a little more specific it would be easier to help you.
2. How to change desktop background?
That depends on which version of PCLinuxOS you're running. You could have a look at this thread:http://www.pclinuxos.com/forum/index.php/topic,74821.msg614572.html#msg614572
(It contains a lot of other stuff too.)
3. Is it possible for different users to use different system languages?
Yes it is (if you by "languages" mean the everyday human ones). But you may have to set up them separately for several applications.
I would have given more detailed answers if you hadn't asked three very complex questions in one single post. Just one question per post, please. Don't be afraid to post multiple times.