I stick the pictures on with a bit of rolled up sellotape on the back to keep it steady as I sew. I use a small notice board pin to pierce the holes through first, and put a mat underneath it to protect the table.
Try and make the stitches all the same size.
Tidy up the ends on the inside.
To hide the stitches get a piece of A4 paper and trim it to slightly smaller than the card. Measure 1.5 inches in from each end on the crease, then another one inch in. Stick the pin in at these places and use four strands of cotton to tie them together.
Then stitch your name on the card at the back.