It seems so obvious, I can't believe no one beat Prettypegs to it... This Swedish company produce quirky, playful legs that screw into the bottom of IKEA sofas and beds, allowing you to quickly, easily and relatively cheaply update your furniture (well, it's cheaper than a new sofa anyway).
Prettypegs allow you to choose your design and colour, and will ship it all the way from sunny Sweden for you to install yourself, IKEA-style.
Their website is nice too - www.prettypegs.se
Rach x