When starting a compost pile from scratch for kitchen food scraps, do I need some kind of starter material? For example, should I take any material from an established composting pile to seed it with appropriate biological agents? If needed, is such starter sold in any stores?
A starter material isn't technically necessary, though a good amount of some sort of neutral, non-food based material (such as leaves, dirt, etc) will help to keep it from smelling like rotten food. Otherwise, the natural flora and fauna will breakdown the foods over time, as long as a reasonable nitrogen ratio is maintained.
It's more important to worry about a good balance of materials ("greens" and "browns" so that you have about a 30:1 C:N ratio) than it is to worry about a starter colony.
In terms of what to use: you can use existing compost, well-rotted animal manures, or healthy soil from your garden. All of these things will have the microbe families that you want in your compost pile.
A starter isn't a requirement, but it can certainly help. A shovel from a long-standing site of decomposition will work.
Manure works really well in a compost pile that includes food scraps, as it provides thermophillic bacteria that like the stuff we eat.
Include plenty of fine carbonaceous material such as sawdust, to maintain the carbon-nitrogen balance. Build the compost pile big so it can get hot. My compost hits 130 degF.
A dead mouse in the compost will attract the right kind of microbes.
It's not essential, but it will speed up the process initially if you use a good mix. Personally I don't bother, but I don't really mind when the compost comes and am happy to wait. If you could do with the compost sooner rather than later, then chuck a load of rich soil or existing composting material in there to get it started - they contain a lot of the necessary bacteria which should thrive on their new found food.