The beliefs and lore and etymology surrounding this word could be spun out into a skein long enough to knit the next Doctor's scarf. We don't have time for that, so I will keep it shortish and hopefully nobody will feel they have to clean the erasers after class.
Arcadia is a paradox; it was an isolated region in ancient Greece reknowned for peaceful pastoral scenes... but also was reputed to be the primary seat of Pan worship. Goats! Sheep! Orgies! Pipes, hooves, horns! The juxtaposition of utter tranquility next to the purest savagery and wildness appeals to me on a fundamental level.
My art is like that. I can't for the life of me produce anything pretty. It is all wild and twisted and fierce in some way; my roses all have thorns, my flowers all look vaguely tentacular and most of my animals have a dangerous gleam in their eyes... even the hedgehogs. So, as you can imagine, the cheerful dissonance of Pan's Arcadia suits me just fine.
As for the unicorn motif... in my world, unicorns are more goatlike than horselike, so that's my tip of the hat to Ol' Goatface packaged in a good-business-don't-offend-the-straights sort of way. With the deepest respect intended, of course. :)