Firepots are traditionally used for making soup or broth, often with vegetables and thinly sliced pieces of meat cooking in the mix. These days, there are two basic types of firepot-hanging and tabletop.
The traditional firepot hung from a hook in the fireplace. It was an ideal implement for cooking soup since soup doesn't need precisely controlled temperatures or cooking times. You could throw in the basic ingredients of the soup and light a fire under the pot. Then you could walk away and forget about it except for making sure that the fire was still going.
These days, electric crock pots, as well as simple stock pots on the stove have replaced the need for a firepot while adding a degree of flexibility and safety to the soup-making procedure. What's left behind is simple romance.
It simply looks attractive to have a small pot hanging from a hook in your fireplace. It calls up memories and thoughts of days gone by when a whole house could be filled with the smell of cooking. A simple black firepot, perhaps with a polished brass lid can provide the sort of homey romance you seek. You may even really want to pursue that romance and cook in your fireplace. If so, make sure that you get a functional hanging firepot and not one that is meant for decorative use only. Sturdy cast iron is a good bet.
Whether decorative or functional, most traditional hanging firepots will be less than a foot wide and less than a foot in diameter.
If you really want to cook in a firepot, you should consider the tabletop variety. It can look like a traditional firepot, though often without the hanging handle. It accommodates an alcohol burner below that will heat the contents of the pot. It should come with a lid that has an adjustable opening to provide a chimney effect. (In the old days, this was done by setting the lid askew slightly, but an adjustable lid gives you much more precision.) Try to find one made of copper since this will conduct the heat more efficiently and more evenly.
The obvious advantage of a tabletop firepot is its portability. You can use it to cook up a soup and then bring it to the table as a serving dish. The fire underneath will ensure that the soup stays warm right up until it is served.
A second advantage to the tabletop firepot is versatility. It can be used for more than soup. You can also use this sort of firepot as a fondue pot for meat or vegetable fondue. You can even use it for cheese and chocolate fondues if you are careful not to scald the ingredients.