Dots, dots, dots. They're a very good fall back option when you're out of ideas and can be varied in both layout and colours, essentially giving you an unlimited number of designs. The first picture below is a combination I've used before but this time in a more stamp-like pattern. I failed completely at taking a picture of the full design, so I only had this one with my (now broken) iPod.
This second design is a bit more elaborate. I was given quite a bit of nail caviar for my birthday but I've been a little sceptic to how long it will last (especially given my current training schedule). On the the other hand, since I now had so much of it I figured I should give it a try. I couldn't find a colour from my collection which matched the caviar perfectly, so opted for three shades of blue. Luckily, the dark blue has aged enough that it's not as runny as fresh polishes are, meaning that I was able to make some smaller dots with it.
I have yet to see how long this caviar lasts, if it's good enough I may start using it more often.