I don't have a child yet but work in a childcare centre plus with our endless supplies of books and such I hope I can help with some ideas
-Blowing bubbles
-Stretching out (great for if your baby still curls up like in the womb). Just do gentle stretching exercises-arms over head and then down, bring one arm up while gently stretching opposite leg, etc.
-Swat the Toy- attach a small cuddly toy or teething ring to a brightly coloured ribbon. Dangle the toy in front of LO and make it sway from side to side, encouraging LO to reach across it's body.
-Rolling over-To help LO roll over place LO on their stomach or back on one side of a towel or blanket and gently lift it a bit, so LO rolls onto their side. Or gently push her back and forth so they learn how to swing their weight correctly.
-Grab out the family photo albums and show baby their relatives.
-Sing some nursery rhymes together
-To help with some crucial tummy time lie on your stomach facing baby and have a good old conversation. It will help baby to become more comfortable on their stomach even though some babies object loudly.
-Pinwheel magic. Grab a colourful windmill and have some fun blowing it while baby watches.
-Paint some footprints also a great keepsake for babies box
-Grab different objects so baby can feel the different textures
-Heaps of verbal stimulation-reading, talking, singing, etc
-Take a walk in the garden, play with the dog or watch the birds
-Play a sit-up game: Pull him up gently and slowly by his arms and then lower him back down. This strengthens his stomach and lets him see the world from different points of view.
-Exercise his legs by lifting them up and then letting them flop down. Try this rhyme to go with the game: "Hippety hippety hippety hop, hippety hippety and then we flop."
-Put him on his stomach and place the palms of your hands on the soles of his feet so he can push against them and slide forward. This will help ready him for crawling.
Hope these help