The MultiView plugin with DLLs from Yahoo Desktop (or similar) may handle QTI images, but I'm not certain.
If you have QuickTime installed and QTI images can be viewed in IE then they might work in Opus if you add .QTI to the ActiveX plugin's configuration, but the last time I checked QuickTime didn't work with the ActiveX plugin. (I plan to improve that in time but it hasn't been a priority since you can view .mov files with the Movie plugin and QTI images are quite uncommon.)