I don't think it's possible with iekELLIPSE (at least in my version of ImageEn). However, you can construct ellipse using iekPolyline (usually using midpoint algorithm) and then you can rotate polyline.
Thanks all. I considered the polyline but wanted to avoid it due to the lot of segments needed to reproduce the curved path of large ellipses. Anyway it seems the only way at the time being.
Nigel, you should consider to add the ellipses rotation to the incoming releases...