Adding flavors to the water will not transfer to the vegetables. Steam is a poor medium for flavor as water carries almost nothing with it when it becomes gas. There are a few very good methods to add some flavor to steamed veggies, so you can just use one of those!
You can add herbs and other aromatics to the veggies This works best with fresh herbs, but a few sprigs of rosemary or a few leaves of basil in contact with your steamed veggies will get some good flavor action. Alternately, mixing them in right after you take the veggies off the steam will let the residual heat of the veg to bring out the flavors in the herbs. Other things that work well is cooking your veggies on a bed of orange peels or lemon peels to add some citrus flavor.
Add oil, plus any flavors you want to infuse into the oil Once you have steamed your veggies, hit them with a light drizzle of oil. I make a chili-infused olive oil that I toss my steamed carrots in that is always a huge hit. There are wide array of lipid soluble flavors that you can infuse your oil with.
Compound butters are great, but so is just butter Animal fats added after cooking almost always turn ho-hum into yum-yum. Butter has long been the french way to add a bunch of subtle flavor to a side dish. You don't have to use a ton, normally a light toss is enough to make a difference. Compound butter is just butter with herbs chopped in and it gives you the double whammy when you use it.
Any ground spice You can also just shake some ground spices on. Pepper, curry powder, cinnamon, pretty much anything that sprinkles and fits the profile you are looking for will work. If your spices are fresh ground, you will get even more taste for your buck.
If you are boiling your veggies, your options open up. Most root veggies will take on the flavor of whatever you cook them in, so using stock or vegetable broth can add some flavor. Vegetables that you cook with each other in a pot of boiling water will also get some transference among themselves. That's the basis for a large number folk dishes like New England Boil and the reason Cajuns always throw some taters and corn in with the crawfish.