design by me 和design by myself 那个是正确的?

都正确
by oneself 意思是“独自地,单独地”
sth is designed by me\him 就是说这东西由我（他）设计,是一种普通的说明
sth is designed by meself\himself 也有前者的意思,但是更强调是“靠自己单独设计出来的”。