The straight streak near top left is likely a meteor. I did an equalize of the image and saw several more squiggly streaks, albeit much smaller.

My best guess is insects. The right hand one that appears to terminate at a star is probably a firefly type pulse that fades as it moves, the top one also fades but no distinct pulse, maybe faced away. To move over that much of the sky so quickly, the insects would have to be close. With so few in the shot, it's quite possible you would not notice them.

---

Edit

---

@Matthew Dearsley mentioned he'd seen something similar in a high altitude aircraft.

One other possibility, but I consider it unlikely, is radioactive decay.

Photographing Radioactivity with a Webcam shows some vaguely similar, but far more concentrated images.

Alpha decay would give bright spots like a star. Beta decay would bounce around giving curved and broken lines.

However Beta decay is readily blocked by the camera body and the lens. You'd have to get some radioactive dust inside near the sensor. At high altitude, an occasional energetic Gamma ray might create a rare scatter directly on the sensor but it's very unlikely and the pattern would be different.

You could try testing for radioactive decay in your camera by taking a series of long exposures, perhaps very long exposures, with the lens cap on and the viewfinder covered to see what shows up in your black frames. Keep in mind that a few stuck pixels would not be unusual.