One retirement party that I helped with years ago was hilariously funny. At the ballroom door, there was a big poster of him (His official office portrait) with mustaches and other things drawn on his face.
It was titled "Don't let the door hit you on the way out." Retirement Party.
Everyone else in the company was at least 10+ yrs. from, retirement and super jealous of his new life of leisure.
Other blown up pics (Costco has a great deal on posters right now in their photo department) of him were placed around the room on the walls. They super imposed his face on the bodies of people doing things like lounging on a cruise deck, golfing, even one of him getting a manicure.
For centerpieces there were items from his office placed on cake stands. With a nicely framed fake certificate placed in front of the stand of who in the office it was bequeathed to and why.
"This Stapler is bequeathed to Peter Smith.
You steal this stapler off my desk every time I walk out of my office. Now its now officially yours. I don't think I'll need it while I take 2 hour naps."
Things like frames were bought cheap, goodwill, yard sales, dollar stores and spray painted gold to match.
Cake plates were made out of goblets and wine glasses turned upside down with a plate or tile on top, glued together with household cement.
If it need to be more formal, you can still do everything, just regular pictures of him through out the years at work.
.