Warlocks are pretty good as is. But they need at least one more invocation.
Eldrich Claws
Prerequisite: Eldrich Blast
If you cast eldrich blast at a creature within 5' of you, you do not suffer disadvantage and increase the damage die to 1d12.
Beyond that, it would be nice if there was some mechanic to tempt you into being "evil", or doing whatever it was your patron wanted.
Warlock of Slaughter:
If you kill a humanoid creature whose CR is less than half of your warlock level, you regain X hit points. (hey look, some kobold children...)
Warlock of Fire:
If you set something on fire, you gain X THP at the end of each of your turns for as long as it burns. Larger things give you more THP. (this is a nice forest....)
Warlock of Deception:
Each time you succeed in a deception check, you gain... (why would I lie to you?)