Check out dietdoctor for their excellent 'visual guides' for what to eat, as well as recipes, meal ideas, etc.
In general, above ground veggies are going to want to be your focus. Leafy greens especially will allow a larger volume - this includes everything from lettuce to spinach, kale to herbs! But you can also do asparagus, broccoli, cabbage, zucchini, cucumber, peppers, mushrooms, etc.
Fruits are a bit hit and miss. Avocado is a great source of fiber and dietary fat. Coconut cream or milk can make an excellent soup base. Berries like raspberry and strawberry have a high fiber content but still should be eaten moderately.
Most of these can be eaten raw, cooked, steamed, fried, or added to dishes for a variety of flavor options.
In general you'll want to avoid most root vegetables, but there are a few notable exceptions like radishes. I've heard they can be roasted and mashed, but I've never tried, I love them raw too much! Onions and garlic tend to be used sparingly as flavor, but watch how much you use if you tend to really love onions. Ginger is another root that can be used for flavoring.
Realistically, your best bets for vegetables will be the leafy greens such as spinach, kale, collards, beet greens, lettuces, turnip greens, etc. along with cruciferous veggies such as cabbage, cauliflower, broccoli, turnips, and kohlrabi - with some radishes for variety. If you are following the 20g NET carb version, then you could likely also fit in some mushrooms, a bit of onion and garlic and tomato for flavouring, and a few berries.
Oh - and search for vegetarian / vegan keto recipe sites for great ideas on including more veggies and healthy vegetable fats. Even if you are a carnivore, the vegetarian / vegan recipes will help you maintain variety and nutrition. One place you might want to start is: www.ibreatheimhungry.com/101-best-keto-veg etarian-recipes-low-carb/
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