You don’t need to decorate the office each day or have morning pep rallies, but the workplace should never be dreaded by employees. People spend most of their waking lives at work, with substantially less time for family, friends and activities they would much rather be doing. By the very definition, they come to “work” and you have to pay them to be there. People have to feel motivated by more than just a paycheck.
Be sure to have a welcoming environment where people feel respected. Celebrate special occasions to break up the routine, but don’t make celebration itself the routine of no work will get done.