Purple-leaved will be a challenge. I've always been partial to Tillandsia australis and rauhii. These are two good sized plants albeit smaller than imperials than do well in lower light situations.

Alc. Vinicolor? They are very deep purple, smaller than imperialis and do fine in filtered light.

Thanks for the suggestions. I was also thinking Werauhia sanguiolenta might be an option too?

Hi anygreen, what light levels are you talking? Werauhias do well in dappled light. As Sid Marx said Vinicolor is great especially if you get colder winters than Queensland. You could even go a Imperilas x Vinicolor.