Yes, that is my stock bag--basically odds and ends of vegetables. The end result is actually quite good. It has the peelings, ends and stems of vegetables as well as the stems of herbs in it (all from either my garden or my CSA). I also included part of an onion that I wasn't going to be able to use before it goes bad.
I simmer it for the better part of an afternoon with a few bay leaves and peppercorns (and maybe some more herbs and garlic). I keep this in my freezer and add vegetable ends and scraps to it every time I cook. It beats tossing the scraps or composting them right away.
Once the bag is full, I make a batch of stock (so guess what I'm doing sometime this week). I'll either can it or freeze it--usually, when I can it, there's enough leftover that won't fit into a canning jar that I end up freezing some, often in ice cube trays. Then I wash out the bag and start all over again.
I'm not picky about the vegetables I'll include--whatever is left over from what I've been cooking. Potato and carrot peels, the ends of carrots and zucchini and summer squash, the tough stems of greens, the peelings and ends of beets, the bottom part of celery or bok choy, the stems or tough parts of vegetables--I'll use them all.
It seems like a waste, otherwise, to just toss them or compost them without this one extra thing. And when I cook, I often replace stock for water--it kicks up the flavor a lot. So if I boil rice, I will cook it in stock, not water. If I make something in the slow cooker, I'll often use stock instead of water. If I make something like curried lentils, I'll cook the lentils in stock if I have it on hand. If I've got stock cubes on hand, I'll throw one or two into something that's simmering on the stove if I want to add extra flavor, or I'll add it to my pasta water--it does add some flavor to the pasta.
Eating vegetarian or eating simply does not mean you have to eat bland food. You may as well get as much use as you can out of the things you have--so I'll extract as much flavor as possible and then compost them. Yes, you can buy stock (I have one container left in my pantry) but this feels a lot more satisfying. It's as if I've sucked up every last drop of pleasure these things have to offer.