Picture lights are filament lamps used in the fittings over pictures strangely enough!
They are also known as strip lights or shaver lights
They are also used in display lighting vanity units furniture and pelmet lighting
They are dimmable
The good news is that these are still available in both clear and opal!
This is one place where fluorescent lamps wont do the job as the light from fluorescents can fade paintings, incandescent ones such as these will not fade anything.
They are pretty simple to identify, you just need to match the wattage and length