Giving your forum an entirely new look and feel is easy — just download one of these great themes! There are even themes for the admin control panel.
Projects in Responsive

MyBB Default 1.8 theme responsive (css grid)

Responsive Modern Mybb Themes 1.8.24

Fully responsive, modern & multicolor theme for MyBB 1.8 (Documentation included)

Fully responsive, modern & multicolor theme for MyBB 1.8 (Documentation included)

A basic Responsive MyBB theme using Bootstrap 3

A flat and simple responsive premium theme for free now!

This is MyBB's default theme with improved layout design for mobile devices.

Dark and responsive theme for MyBB 1.8 by Marihunaen.

The Agood theme was designed for MyBB 1.8.21+ series.

eXe is a mobile compatible and desktop mybb theme.Applies to Mybb versions 1.8.X

Responsive and multicolor ACP theme in Flat Design
Purple & Black modded ACP Theme
MT MODERN THEME

Cheater theme, very basic and my first theme.

Seriforn is a light MyBB theme, which is highly compatible with most of the popular MyBB 1.8.x plugins.

Impulse Dark is the sister theme of Simple MyBB Variant Theme
MyIPB is a clean and elegant theme, covering the awesome style of IPB 4.x.

Free Responsive MyBB Theme - NetPen