Add eggs to the smoothie, like doing the egg coffee; I turn mine into a smoothie or frappucino usually. Also, coconut milk in a smoothie ups the fat. A new thing I've been eating obsessively (ill get sick of it in a few days ) is 9% m.f. Greek yogurt (plain). It's insanely delicious and high in fat and protein. There are 10 carbs per serving, so its about my highest carb load, but only 2 are sugar. For the protein and fat, and that I know its a treat, I'm okay with that.
There are good no/low carb proteins out there. Unflavoured whey, Only Protein, and if you don't mind artificial sweeteners (secondary to stevia in the ingredient list) Promasil; then there's egg protein, and goat whey.
You can add avocados, some coconut butter, maybe a bit of nut paste as well?