In my ubuntu 11.04 customized
doesn't show ubiquity's welcome screen, directly start desktop where install icon appear.
If you are trying it from a USB Live System witout using the recommened "Universal USB installer" or usb-creator-gtk, it is not unexpected.
I make an Ubuntu iso bootable by extracting it's content in a pendrive. Then use
sudo syslinux --install /dev/sdb to create an mbr. then renaming isolinux folder into syslinux folder, then booting from the usb. In this case a welcome screen is show.
But if you are trying to boot using grub2, you most probably use this kind of command or entry in
root=(hd1,msdos1) linux /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- initrd /casper/initrd.lz
this case you have to put
only-ubiquity in the
linux line (2nd line).
so that the line becomes
linux /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity initrd=/casper/initrd.lz quiet splash --
Hope this will help