Cube (small) your own bread - I use stale crusty French bread. Saute in 1/4 lb. sweet butter the following: chopped in same sized pieces - onions, celery with leaves, carrots, fennel bulb, shiitake mushrooms. Toss with the bread, add copious amount of Bell's (poultry) seasoning (New England product). Add some dry sherry to your chicken/vegetable broth. (I have't found a veg broth that I like) I also add slivered almonds for crunch and flavor.

I make this all the time for the vegetarians at the table. I do something similar to the above, except I focus on the bread and use fresh herbs for maximum flavor. The rest of the prep is typical.

Cube light sourdough and toast in oven. A strong tasting bread helps here.
I also agree on the upping the butter content.
Add chestnuts if you want something with a meaty texture.
Add fresh herbs generously: primarily sage and parsley, a little thyme and rosemary. The fresh herbs help here with the intensity.
Stock: I've not found an ideal brand but I do use the Imagine "no chicken" broth. It doesn't have the strong tomato flavor that is so wrong for T-day, but it is lighter. Making your own broth is easy enough, though, and you can control the contents.

Tons of chopped onions, celery & mushrooms sauted in lots of sweet cream salted butter, sprinkled with a massive amount of Bells Poultry seasoning, pour all this over a lg box of Bell's Stuffing, toss, pour a good 2 cups of homemade (if possible) vegetable stock, into a buttered baking dish, cover with foil (we DON"T like the hard crunchy stuff) and bake. Best ever & the only one my family truly loves for Thanksgiving & Christmas.

Do you/they eat butter?

Just wanted to say, if you want to add 'meat', you could use vegetarian sausage.

I agree with all the posters who said to make your own stock. I've yet to find a ready-made vegetable stock that didn't taste heavily of tomatoes. I haven't tried the brand Gooster recommended, though.

I have never made any stuffing other than my carrot stuffing.

I usually make it with chicken stock, but I have made it with vegetable stock (Pacific low sodium). It is always a hit. The carrots make it sweet, the butter makes it good! I also make in in muffin tins so that you get more crust surface.

As far as bread cubes, go to Whole Foods. They cut up leftover bread from their bakery, often assorted if you want and it is so so so good. Plus easy.

Carrot Stuffing

Serves/Makes:2 qts. of dressing; about 24 standard muffin/cupcake size, each 1/2 cupIngredients

• 1 1/2 sticks of salted butter
• 2 cups diced celery
• 2 tsp poultry seasoning
• 8 cups. stale bread, cubed
• 1/4 tsp pepper
• 1-2 cup turkey broth (I steep turkey or chicken bones in store bought organic turkey stock, w fresh herbs, and strain) or vegetable broth for vegetarians
• 1/2 cup finely chopped onion
• 2 eggs, whicked
• 2 cups grated raw carrots (washed and peeled)

Preparation

• Place onions and 3T of the butter or so in a frying pan
• Stir occassionally until onion is soft and just starting to brown.
• Add celery and carrots and rest of butter, and cook over low heat until soft
• Mix in seasonings and two raw eggs
• Add onion, celery, carrot egg and butter mixture to bread cubes.
• Pour turkey stock gradually over the mixture stirring lightly (do not mash bread mixture.) Add as much as you need to make the bread soft but not soggy
• Add more seasoning if desired.
• Using a 1/2 c measuring cup, scoop the stuffing into buttered muffin tins, and press down firmly
• Bake in a 375 oven for 12-15 minutes or until browned. Let cool in tin

I wing my stuffing but I do it much like those above.. but the best I ever made was using a sourdough pumpkin bread from Le Bus bakery. It was sublime.

I totally agree on a mushroom base for the veggie stock. Dried porcinis work great.

I've tried a few variations of this stuffed pumpkin recipe . It's really rich and looks great on the table. You can omit the bacon to make it vegetarian: http://www.epicurious.com/recipes/food/views/pumpkin-stuffed-with-everything-good-361169 

For a basic stuffing, I like to add chopped mushrooms and dried cranberries. Yummy.