Upload screnshots for default theme. You can not download this theme from somewhere.
Yes, every tagged mail has a label in subject, like in Google Mail. What version roundcube you use ? Do you have any javascript errors ?
I’m using Roundcube 0.5.2. I just checked with Chrome’s JS console for errors, but none where displayed. Since my installation is quite new, I don’t think I have mis-configured anything. (Active plugins: 'markasjunk2', 'drag_upload', 'custom_from', 'smart_self_reply', 'message_label', 'jqueryui', 'keyboard_shortcuts') I will try a fresh install with 0.5.3 tomorrow.
In Gmail I'm don't use manual way, I think it is possible to realize too, once.
That would be great, if it could be done. I did not test it, but the way the “label” plugin looks, you set the labels (tags) manually? This behaviour added to “message label”, and my almost perfect webmailer is done. :-)