The Telework idea is great but may leave out those who are not telework eligible or don't have an agreement in place. Although 'Time-Off Awards' may be off the table as an Agency wide policy, supervisors still have the authority to grant employees up to 1 hour of Admin Leave without submitting award nominations.
In my experience the best no-cost option and best morale booster is recognition for a job well done. Supervisors and managers should be personally expressing their appreciation to employees regularly and even if a plaque cannot be issued an all employee email or and/or posted notice identifying and thanking an employee for an exceptional accomplishment goes a long way to boost morale. This can also be done on a more regular basis with 'Employee of the Week' or 'Employee of the Month' announcements.
Such accolades can also be effective when a higher level manager or executive mentions an employee's accomplishments in a more public forum such as on the Agency's website or during a public speech or meeting.