Gebnerally, I think of eldritch blast as being a mechanical representation of the rays Doctor Strange uses in old comics, like this:
But I had a PC GOO warlock who followed Shub-Niggurath, the Lovecraftian embodiment of untamed and unstoppable nature and growth, and that character's eldritch blast manifested as a mess of branches, leaves, and vines bursting forth from the target's body. That was a cool visual.