Whoops, somehow I missed this when it was first posted!
Nothing wrong with repeated rhythmic octaves in the left hand to drive things forward. In fact, that's one of my favorite kind of accompaniments!
Even though there weren't a lot of crazy effects, as you call them, I do like what you did with sustaining certain notes in the beginning of the melody to kind of get that pyramid effect.
Somewhere down the line, I think it would be cool if you were able to flesh out parts of the melody with some chords and harmonies. I know, I know, easier said than done, but since - if I remember correctly - you're recording the two hands separately anyway, you might be able to play around with adding another track or two.
Nice arrangement!