What a fun question! First off, the fact that you have already been engaging in nipple play means that you have a head start on knowing what your partner likes in terms of pressure, sensation, etc. - and that's awesome! Now, here are some ideas to take things to the next level. When it comes to toys, the most obvious starting point is nipple clamps. Available in a variety of sizes, shapes and intensities, and with add-ons like chains for pulling, weights, and even small vibrators, there are many options for giving your partner a continuous squeeze while you play. Additionally, nipple suckers can be a lot of fun. They fit directly over the nipple and use suction to increase sensitivity. My final product recommendation is a small vibrator that will allow you to focus vibration directly onto the nipples. Anything from a bullet vibe to something you can wear on your hand to transmit vibration directly from your fingers like the Jimmyjane Hello Touch will do. When it comes to techniques, temperature play can be a lot of fun. Ice cubes or warm wax from a massage candle (make sure to read the instructions so as not to burn your partner) can create wonderful sensation. To make it a bit more hands on, you can put the ice or some warm water in your mouth and then apply your mouth to the nipples.