As I switched back to 1280x800, I felt the previous theme was too big to show more than 5 tweets a page. So I just modded the old one a little bit into a micro edition.
To install the new gwibber theme:
1. Download the new theme from github
2. Decompress it to ~/.local/share/gwibber/ui/themes/
You should end up with a folder called gwibbiquity-micro with a few files inside it.
Make that path if it not present
3. In Gwibber, open Preferences (Gwibber->Preferences or Ctrl+P).
Pull down the theme chooser and choose ‘gwibbiquity-micro’.
4. On my system, it took Gwibber a few seconds to apply the new theme.
Be patient, and things should shape up.