I really like Pepper and Zephyr. But, if you're into people names for horses and just don't like Ivan, the English translation is John! Or maybe stick with Russian and go for Tsar... He looks lovely and very sweet. I hope you have lots of fun together whatever he gets called
If the Ivan dude is from Kiev, as another poster found, how about Kev? Or, I also like Pepper because of the 'epper' sound in his registered name. And also that peppers can be red too.