GPRename is a GUI tool based on gtk2-perl in Linux.It can easily rename multiple files or folders,it supports change filename in lowercase/uppercase,insert remove or replace letters in filename include the extension,change filename to number.
Install GPRename in Ubuntu
Just search gprename in System->Administration->Synaptic Package Manager
Or open terminal from Applications->Accessories menu,and type this command to install GPRename:
sudo apt-get install gprename
Now,you can launch GPRename from Applications->Accessories menu or by type
In the left,choose a directory and in bottom do what you want to change with these files/folders in this directory.Click Preview and preview the changes in right box->New Name.Finally click Rename button to do the change.
GPRename source page:http://gprename.sourceforge.net/