I found these insect shells under a printer which was stored under a table, and there seemed to be hundreds of them. I checked around the area there didn't seem to be any live insects. Would appreciate your advice, thanks!

Without some idea as to the scale of the picture, best guesses would be egg cases from German Cockroaches (5-10 mm or about 1/4 inch long) or the molted exoskeletons of drugstore beetles (1 mm or 1/16 inch). If that's a regular quilted paper towel they're on, go with the beetles.

Here's a link from WSU that has a remarkably common sense approach to the beetles:
Drugstore beetle

Thanks for your reply! I was worried that it might be termites. Actually it seems more likely to be the cockroach option. This was in the bedroom (where I also see cockroach feces, especially in drawers and where I keep some old cloths which haven't been used in a while). I don't have cockroach problems in the bedroom but tons in the kitchen.

You mentioned these were under a printer. German roaches love to hide in electronics. The circuits stay warm and the circuit boards are mounted at just the perfect distance to make Mr. Bug feel all cozy and comfortable. Getting them out of electronics is easiest if you are in the Northern hemisphere where it's winter right now. When the temperature is due to get below 36 degrees Fahrenheit put the device in a moisture proof bag outside overnight. Bring the device but not the bag back inside before it warms up. Throw the bag away.

If freezing is impractical, baiting is the next option. Use the gel baits all over the home, along cracks and crevices about every 12 to 18 inches apart. Don't use too much in any one place. The fingernail on your little finger will hold six bait dollops of the proper size. Some of the commercially available gel syringes will tell you to use larger placements as their products are also often used for the larger American and Oriental cockroaches.