Is it possible to make an entity without a model? Entity in the form of a moving picture

This is technically possible.

HOWEVER, this does require custom models.

Tutorial on how to do it:

Step 1: Make a new model in blockbench

Step 2: Set its Z size to 0.01 (NOT 0, or the texture will be really buggy). You should also probably set its Y and X sizes to 32 (this is what I used to create nextbots)

Step 3: Set the texture size to, say, 64x64.

Step 4: Import your picture.

Step 5: Half the texture size

Now, you should have a working nextbot-like model!

(Yes, I know this was from October. I still want to answer this question though.)

Wait, if this is Java edition you need to do z size is 1

*Z size needs to be 0, sorry about that

Oh wait, Blockbench rendered the model wrong...

REAL TUTORIAL:

Step 1: Create a model in Blockbench

Step 2: Make the model have dimensions of (insert x) (insert y), and 0 z

Step 3: Make the texture size 64 or something, big enough to fit the entire model or things will get weird

Step 4: Get your PNG and put it into Paint or any other photo editing program.

Step 5: Multiply the picture's dimensions by 2. Make sure you don't change the actual size of the content, only the picture's dimensions.

Step 6: Import the PNG

Step 7: See how it looks (Feel free to tweak the picture if things look off)

Step 8: Export the finished PNG and model

Step 9: Congrats! You have a finished PNG model!

Actually, don't use Paint. It removes the transparency of the image...

And one last quick note, this won't just face the screen like actual nextbots. They are just flat like them.