Well the smallest fraction of a Bitcoin is 0.00000001 BTC which is referred to as 1 satoshi. If you don't want to use decimals, you can always use satoshi for small amounts. I personally tend to think in satoshi for amounts less than 0.001 BTC, so for example I'll refer to 0.00042000 BTC as 42k sat. This is obviously not ideal but for now it's fine for me. I'm sure the devs will think of something as Bticoin adoption rate goes up around the world. Also, the decimals are only scary/confusing in the beginning, you'll get used to it soon enough