hala!, ngayon ko lang to nabasa, usually ikaw ang gagawa ng cover mo, the design and everything, usually ako sa photo shop nag edit, minsan pixlr (anyway they're just the same)...i only know the basics about editing, enough para makagawa ako ng sarili kong covers na satisfied naman ako. If you want to change the pic/cover of your story, una mo munang i-edit yung original pic/cover nya manually bago mo i-upload ulit, kasi wala pang tools ang wattpad para sa mas magandang cover maker (meron naman pero it's not as good as you'd like, saka super limitted yung designs). After mo maincorporate lahat ng gusto mong changes doon sa original pic mo, pwede mo na mapalitan yung cover ng story mo, just click: "Create" then you can see yung list of work/s mo, then click mo yung picture ng book mo na gusto mo palitan, tapos "Upload"....if you want na saktong sakto ang pagkakasukat ng cover mo doon sa book then you should follow the dimension given by wattpad na 256 x 400.
That will be your first option, yung ikaw ang mismong gagawa, but if you don't want na mahirapan then go to "Multimedia Designs Club" marami ang nag offer ng free cover making doon. Just fill them in the details ng gusto mong kalabasan ng cover/pic mo,,, here's the link : http://www.wattpad.com/club/30-multimedia-designs .... the goodness of it, ikaw din ang mamimili ng designer na napusuan mo, maraming designer na magagaling doon, and pwede ka rin mag hire ng di lang isa it depends on you, kaya mas marami kang choices kung ano ang gusto mong magiging result ng pic mo.
P.S Sorry talaga late reply, di siya nagregister sa news feed ko, buti na lang i checked your account. @kalo_gale