The word “Photograph” literally means “Drawing with Light” and when you are dealing with dark backgrounds and long exposures, you can have some fun with how you add some light to an image.
A white or red headlamp will give a subtle glow if you give it a quick wave over the subject. Hold it in place a bit longer for a stronger effect.
Colored gels let you layer in other colors as well, or you can stack several frames as a composite using software. Just pick a color that fits the mood of the image you are wanting to create, then experiment away!
Get a camera with manual settings and put it on a tripod or a sturdy table in your backyard at night with the lights out.
Set the aperture to the highest number (such as f/22), the ISO to as low as it will go (such as 100 or 200) and the shutter speed to around 10-20 seconds.
Click the shutter to open it, then run around with a flashlight or spotlight elements in the garden until the shutter closes.
Have fun with it!