hand-drawn cards are so endearing and make whatever ur saying that much more meaningful! the drawing doesnt have to be perfect or even that good. i treasure the stick-figure cards my 16yo brother who cant draw gives me on my bday. you can also buy a sketchpad of postcard size paper (around 4x6 inches iirc) and then make ur own postcards to send to friends whenever ur thinking of them! as long as its the right size usps will accept them, u just have to draw the lines on the back and add a stamp 👍
edit: omg also added bonus to this is being able to tailor art to the receiver's interests- this card is for my grandmother hence vintage looking flower pattern but u could make cards themed around shared interests or inside jokes or whtever u want