I've read your request for an ambigram-style approach, and so that is what I have created for you.
The letters "FN" have been combined in a letterform ambigram, one that can be used as a standalone icon if you wish. I've enclosed it in a radiant pattern of dots, to signify its comparison to something precious that sparkles (like jewelry). In one submission, I even used Tiffany Blue to help promote your brand as a luxury brand.
I'm happy to make any revisions you require. If you have any requests for a color change, for instance, please let me know.
All entries are 100% vector-based creations, and with the source file you will be able to have any design scaled as large or as small as you wish, without any distortions. I will also provide them in any format you ask for (PNG, JPG, TIFF, AI, PSD, PDF, and any others you desire).
I look forward to hearing your thoughts on these entries. Have a great night.