Here are a few super simple suggestions, nothing super fancy.
-Warm cabbage salad:
Cabbage sliced thin (chiffonade or shreddded) toss with a bit of olive oil, salt and pepper. This is roasting, but I just pop it in my toaster oven on a piece of foil and only takes a few minutes. Take out just as it gets golden brown but still has some crubch/texture. Incredibly simple but tastes really great. And can add whatever seasonings/oils you like.
-Ginger/chili mashed sweet potatoes:
Dice/grate up some ginger. Peel potato, cut into chunks, and either steam or boil whichever you prefer, until you can stick a knife through a chunk but before they get too soft. Put in bowl with ginger, and add chili of choice (cayenne pepper, diced chipotle pepper, ancho chili powder would be good choices), add some milk or coconut milk, salt and pep and mash it up! I've added some cream cheese to mine, you can add butter but doesn't really need it. Pretty amazing flavor combo.
-Rice bowl:
Not exactly a veg side, but steamed rice, with a fried egg(runny yolk!), avocado and some of your preferred hot sauce is a tasty combo if you like runny yolk.
-Curtido cabbage slaw:
Sliced/shredded cabbage, sliced onion, cilantro. Add vinegar, oil, salt, pepper, lime, cayenne, brown sugar. Toss together, goes great with tacos or mexican or anything spicy or fried.
-Bean salad:
Black beans (from a can-rinsed and drained- can cook in a pot with some garlic, onion, cumin and a bit of water or just use 'em straight), diced tomato, diced jalapeño, diced red onion, corn (roasted if you can), cilantro, diced avocado, lime juice, salt and pepper. Can toss with a simple vinaigrette, add in a small blob of ranch dressing if you like. Could also take these same ingredients (maybe toss in some squash or green pepper) and saute in oil.
-Curry tomatoes:
Saute diced onion till soft, add garlic, tomatoes (good quality canned or use diced tomatoes), curry powder and cumin. Any sauteed veg can be added to this, can also use a curry paste instead and toss in some coconut milk and ginger.
-This website 101cookbooks.com has a plethora of veg recipes. There is a whole section of sides.
-If you want to avoid using a lot of cheese, consider trying nutritional yeast A lot of vegetarians use it, it gives food a salty/cheesy taste.
-Also, learn some basic flavor combos/techniques to make a good sauce. Often you can use the same veg and transform it many ways by changing the sauce. A few examples:
-Sesame oil, soy sauce, ginger, honey/brown sugar, chili (sriracha or diced chilies)
-Add some peanut butter or tahini to above.
-Avocado, rice wine vinegar, olive oil, garlic, cayenne.
-Rice wine vingear and sesame oil.
-Greek yogurt, lemon, dill, cumin, cayenne, salt, (honey or brown sugar if yogurt is very tart), salt and pepper, turmeric.
-Ranchera salsa: roast tomatoes, garlic, onion and jalapeños and blend it up.