I worked at a bio tech company for many years and some people dressed up, some didn't.  It was up to the individual.  There were cubicle decorating contests. Thinking aback it was very fun.  I never dressed up, maybe a funny headband that was the extent of my dressing up.  I did have a very cool cubicle, I had this voice activated ghost hanging from the ceiling.  The guy in the cubicle next to me had this thing that would play the Monster Mash.  Between the two voice activate gadgets and some decorations it made for a festive time.  I have great memories.  I am not sure if they do anything like that any more.