How can you write what you see in photo?

Can you say 'curve down' and curve up' or does curve imply pointing downwards?

Here is a picture:


Which of these are possible?

My fingernails curve upwards/up.
My fingernails point upwards/up.

My fingernails curve downwards/down.

My fingernails curve. (Does this mean 'point downwards'?

What is the opposite of the picture? Upward?
Thank you