Moebius is perhaps the most obvious example but his art cannot be recomended enough!
Ioannis early art is comparable to Roger Deans. see here:
http://www.dangerousage.com/digital-art/nggallery/Michael Whelan has likewise done many illustrations of fantastical landscapes
You should definitely check out
Max Ernst and his contemporaries of the the Dada and surrealist movements ( It's an interesting point in western art history anyway). example:
http://uploads3.wikipaintings.org/images/max-ernst/the-eye-of-silence-1943.jpgPeter Elson does superb Sci-fi illustrations! Investigate!
Zdzisław Beksiński has done some fantastic twisted images and landscapes, superficially similair to HR Giger, but that might be a tad darker than what you are going for?
Dan Seagrave makes wonderful Heavy Metal covers often in twisted, alien forms, look out for some of his personal works.
Hans Arnold is a wonderful artist but not enough of his work is available online.
These are just at the top of my head, but remember that many classic Fantasy artists( like Whelan) also did a lot of sci-fi work so they are worth checking. Don't have links for everyone but they should all be easy to find on google.
Also here is a great example from Real life!
http://www.binscorner.com/pages/s/strange-plants-of-socotra-island.html?z=10