I've never offered a foraging bowl with non-foods. Not to say Snickers doesn't put non-foods (usually shredded cardboard/paper --even cotton rope or fabric bits) in his dishes sometimes!
I do try to offer a varied bowl through-out the day. And for his main meal, I completely cheat and add thawed frozen veggies to his fresh mix -- plus rice which he prefers over pasta (though I do toss in some pasta in a few times a week with mixed results). He always has a bowl of Zupreem pellets available in his other dish (which he likes okay) and I offer a tablespoon of seed a few times a week (so thankful he's not a seed junkie!!!)
His fresh veg/fruit bowl (incl some frozen veg) I feel needs to be removed within 4 hours or so (sometimes sooner). Thankfully he's usually eaten 50 - 75% of it by then. Don't want him to get sick eating food that sat out too long.
For treats, he's fairly happy with Cheerios, peanuts, raisins and unsweetened banana chips.
I just try to keep something interesting in his dish through-out the day (hence treats). I also share my meals when they appropriate for him (not pizza, sorry Snickers!)