No you can not. From the technical point of view possible, but it won't be "Useful".
The alt attribute is used only to specify alternative text to the images/forms, in prose.
Google is expecting the text in CamelCase will be in the tag
Simply put, you need a descriptive text to the image if it is not available for robots and screen readers.
Not every screen readers can properly read a text that you want to put inside.
the image must be necessary, but not necessarily in it something to fill.
If you don't know what to write in the attribute, Google recommends to create one, and leave empty.
My advice to you, better not touch it at all. Just leave it not filled in, for your own good.
Is there a difference between the img card, imgCard, img_card
There is no difference, they are all three bad. Correct answer: An image of a card
or Picture card