You can create and Modify ISO9660 files (iso images) graphicaly in ubuntu by using an open source Linux application ISO Master
Features:
1. Create an ISO image from scratch.
2. Add or remove files and directories to a CD iso image.
3. Make bootable CDs
4. Support for Rock Ridge and Joliet file names.
ISO Master can read .ISO files (ISO9660, Joliet, RockRidge, and El Torito), most NERO .NRG files, and some single-track .MDF files.
$ sudo apt-get install isomaster