Hi Shirli,
in case you have not found a solution yet and still want one: for some other reason i got interested in the shell too, and first thought, this one's solvable with a custom ShellHeadItem. It seems not, because ShellHeadItem has no own renderer, but gets rendered by the ShellHeader. So i tried a bit to find a workaround, here it is (see comments in code): http://jsfiddle.net/sok_/3nnwfouk/
Still note, it is a workaround, it relies on the current dom structure of the shell header + items, which might change.
I think, the "official way" would be to provide an own Header (there is a setter for a custom Header in the shell) that suits your needs.
best regards, Sophie.
PS: make sure you don't get arrested by the UI police ;-) as they seem not to have intended texts in the shell header....