This doesn't answer your question directly, but spices are only a small part of the picture.
Below are some techniques to get more flavor in your soup.
Longer Cooking
Depending on the type of soup you're making, you may just need more time.
Some flavors just need more time to get out.
This is especially true of meat and bones.
It's possible to make a ham and pea soup in an hour, but simmer that ham for 3 hours
and it's night and day.
Rest
overnight Many stews, chili, etc.
seem taste "better" the next day.
Give an overnight rest in the fridge a shot and see if the flavor improves.
Add volatile flavors later
There is a caveat to go along with longer cooking.
Some items work over long cooking times, while others lose flavor.
In addition to meat/bones, garlic, onion, bay leaves (and others) benefit.
Many fresh herbs, pepper, vanilla, saffron (and others) lose their flavor from the heat.
If you are cooking for a while, you might try adding some more volatile flavors later in the process.
Add salt
early Salt helps to extract flavors, so add it early on in the process.
Do be judicious with it, however.
Long cooking tends to concentrate flavors, so you can easily make it too salty.
Sweat vegetables / brown meat Before getting any water involved, sweat your onions, celery, peppers, mushrooms, or whatever vegetables or playing in this game.
Likewise, brown your meat.
The maillard reaction is necessary for developing great flavor from the meat.
cooking.stackexchange.com/users/4489/Ray
Soup making usually involves two steps: Making the broth Adding the particular ingredients that make it an XXX soup.
As far as I'm concerned, the first step is the critical one.
Here are my broth-making tips: Ingredients: Bones with a bit of meat on them.
1 carrot (peeled, whole) 1 Celery Stalk (whole) 1
Onion 1 clove garlic 1 Bay Leaf Marjoram (optional).
-- Thank you Polish Mother-in-law for adding this to my repetoire Steps: Brown
the bones, particularly beef orveal Dice and Brown the onion inbutter.
Throw everything in the pot,and cover with water.
Bring to aboil, and reduce temp to a slowsimmer.
Simmer until it tastes good.
Remove veggies and bones.
If desired,strain broth to eliminate onions andprotein globules.
cooking.stackexchange.com/users/1148/Chris Cudmore
I have several suggestions, also: I feel that adding fried onions or garlic adds a lot to soup giving it spicelike taste addition.
I really like adding Za'atar to soups, especially fish soups.
cooking.stackexchange.com/users/2358/SurDin
Lemon juice works well with a variety of soup flavours, when added just before serving.
I also find that you need less salt when using lemon juice at the end.
cooking.stackexchange.com/users/2939/KimbaF
I had the same problem as you.
You could try adding a bouquet garni , which contains: Parsley Bay Leaves (Laurel) Thyme Celery Rosemary
If you have them fresh, you can tie them together using kitchen rope and toss them in, and remove them after boiling.
If you have them dried, you can (of course leave them in).
cooking.stackexchange.com/users/3721/Izzydorio
Romano cheese is really good on soup, especially with black pepper.
Mmm.
If you're going for a savory taste, add bay leaves and some dill.
Dill also works really well with cream of potato.
Basil adds a little bit of taste, too, but it works best with something tomatoey - you can buy little cans of tomato sauce and put them in if you want to thicken your soup.
cooking.stackexchange.com/users/4861/tim
try some nutmeg in your soup.you can get excellent results in broths, stocks and creams.
for beeth or chicken stock, also try pimento and juniper, mace, bay leaves and parsley.also try a dash of sherry in your bouillon or consommee...
(yammy yammy)
making stocks: do not brown the onion with any fat, just dry brown them.
when cooking soup, just let it simmer (a soup should always be smiling)
cooking.stackexchange.com/users/None/
I've been experimenting with soups recently and trying different recipes, and I've found that I often come out with a good soup that's a bit too bland in taste. And yes, salt and pepper makes a huge difference... but it needs something else. Beyond finding the right spice for the right soup, what are some general things that I can do that won't greatly change the flavor but will add some fullness to the flavor?
How do I keep soup from being bland?
cooking.stackexchange.com
<spices><soup>
cooking.stackexchange.com/questions/12500
cooking.stackexchange.com/users/4853/clueless
Try cooking the soup for longer, and adding fried onions or garlic, lemon juice, dill and bay leaves or a bouquet garni, which contains parsley, bay leaves (laurel),  thyme, celery and rosemary. Salt helps to extract flavours, so add it early in the process. Try cooking for longer with salt and herbs. Add fried onions and fresh herbs at the end.
You could try cooking it for longer. Try adding salt early in cooking. Add fresh herbs near the end. Fried onions, lemon juice and herbs like rosemary, bay leaves and nutmeg for extra flavour. Try using Romano cheese.