I will not suggest a space heater for a un-modified RV because the outlets they use are not all that good.
I added a pair of 15/20 amp house type outlets, these mount in boxes (so you need a spot in the wall where you can put a box) they are fed with 12 ga wire and they each have a breaker all to themselves.
Once you do that most any electric space heater will do.. Hot wire, Ceramic, Oil filed, your choice,, Some folks will tell you one or another kind does a better job of heating but the fact is all electric heaters put out exactly the same amount of heat per watt... Forced air types circulate it better. I kind of like Ceramic cause they are small and perhaps a bit safer,, Make sure whatever you use has tip over protection.
But remember a 1500 watt heater puts out the same amount of heat no matter what kind it is.
Camping world, and I think ACE hardware, both have a nice little electric fire place, Not that big (perhaps a foot wide) 1500 watts and nice flame video.
My computer has a nice flame video.. Very little heat though :)