To capture scenes in low light for lighting decoration, which digital camera model to use ?

i run a small business in lighting decoration designs, iam making a web site for my designs but i need to photograph my designs

I use a Nikon D40. It does well in low light with a closeup lens. I'm not sure what kind of money you want to spend on a camera though. Just remember, point and shoot cameras don't usually offer any settings change like shutter speed and things like that. DSLR's like the D40 can do just about everything.

I have a Pentax K100, I haven't used a D40, but by all accounts they're good cameras. I would imagine that any digital SLR would work, whether Cannon, Nikon, Sony etc. Capturing low light scenes sucessfully depends on camera settings and lenses, which any DSLR can do, but like cantc17901 said, most consumer level cameras won't let you tweak the setting you need to. A fast lens, the correct ISO and aperture setting are what's most important.

In simple terms you need a lens with a wide maximum aperture (imagine the way your pupils get larger in low light), ISO setting adjust the way the sensor responds to light - higher #s work better in low light, but are more grainy so you need to adjust the right balance. The aperture setting lets you adjust how wide your lens aperture (think pupils) opens.

Anything would do. It is not WHAT equipment you have, but HOW you use it.
However I would choose a reflex (they have more features, like keeping your shutter open after the flash went on, so you get both foreground -short-range- and background correctly exposed).
For example you can find a quite cheap Canon EOS 300D or 350D on eBay.