Getting a fab foreground is as much a challenge as it is shooting the lights - imo - with large tour buses, it's unlikely due to their limits on where they can stop. The mini buses are better as they have a bit more flexibility, a private tour with a photo guide and an all terrain vechile is good but also pricey - best of course is having your own car and doing some research in good places for foreground, in a range of places that you may be able to get to with the lights. I liked chasing the lights myself and trying to find a good spot, it was exciting, but i lacked the research and only after the fact did i think of some places i could have gone (this was near Vik). Driving in the middle of winter isn't always a thing people want to do (i know i don't) so I always say to people that September is a good time of year to go as the lights are out, but usually the snow has not arrived so you are less likely to have to worry about that (obv wind and rain can still happen but if snow/ice isn't your thing, september is good). On that occasion I ended up at Skogafoss, but in hindsight, Seljalandsfoss may have been better. i couldnt take full advantage of having the waterfall in shot as the lights were too low, thee was more spray as you got to close due to wind and also the foreground was full of tents and cars which kind of jarred too. i was too scared of driving another 30mins or so down the round in case the lights went.
im no expert but just my experience...