Add Glyphicon to titles?
I think you're on the right track with adding a second custom field to allow the user to choose the glyph.

Once the user has set the title, selected the glyph and saved,  you can merge the two using a template file.

https://api.drupal.org/api/drupal/modules!field!theme!field.tpl.php/7

The one you'd want I think would be named something like this:  field--title--basic-page.tpl.php

In there, you can stick the value of the glyph next to the title.  Does that make sense?