My 1-year-old DS has an absurd amount of toys, so I tend to have them on a rotation. He has several toy boxes scattered around the house, so I change the items around daily, otherwise he gets bored.
Yesterday in the lounge I had a selection of musical instruments in his box, so we had a music day. We did singing/signing, danced to a couple of CDs, played with the instruments together. Music is so so good developmentally! Today in the box are a big pack of megablox, a wooden 'tool kit', a couple of books, and his wooden car set.
He has a ball pool that I get out a couple of times a month. I have a little teepee that I put up every now and then, and we make a den... He's really into playing pretend at the moment, so I bought him this little tea set, and plastic food that we get out sometimes. They were super cheap, but he loves them.
We paint quite a lot too! I make homemade paint using food colourings, water and flour. It's edible.. I just lay a big waterproof sheet down on the floor, strip him to his nappy, place blobs of paint on scattered bits of card and let him so his thing.. There are recipes for homemade clay and playdough online too if messy play is your thing.
Honestly though, I find going out with him is more stimulating than anything else, even if it's just to the park or swimming.. Toddler groups are good too. We go a sensory one each week and he gets so much from it.
Sorry for ranting. I hope something I said helps.