Hello Mandy Hayworth,
ACE has a great youth fitness program; check that out as Ariadne Greenberg suggests.
Do you talk to your kitchen staff? They probably get many posters that are not in use.
You may also want to check out:
NAPS 2 B Fit
One source you might like for ideas, if you do not already know it
Another source to get some nice healthy eating graphics
Do you have a recess walking club? My son’s school did, and they would post about who completed certain levels. The course was marked out and parent volunteers manned a station where they would punch the kids’ cards as they went past. Some of the athletic types ran, some of the kids walked in pairs, but even shy kids who felt awkward at recess had a defined thing to do …. that also made them healthy. If you have programs like that it is a motivating thing, even if you did a weekly pick of a different walker.
Or you could do recipe contests and post them
Or maybe do a colorful display of a sport/activity of the week: karate, race walking, fencing, dressage, yoga on paddle boards, curling…. just introducing them to ideas about types of activity beyond the ones with which they are most familiar.