Luke:
The one thing Luke would hate is confrontation, so he’d try not to be bothered that Calum would be your lockscreen. He’d actually laugh it off the first time he’d see it, but he’d actually be paranoid wondering why you’d even want is best friend as your lockscreen. It wasn’t even a selfie - just a photo taken by some fan or someone in the media stalking him one night.You’d actually notice him be a little edgy every time you’d unlock your phone in front of him so you’d ask him what’s wrong, not thinking of the wallpaper until Luke actually admitted it. You’d sigh and actually be shocked that you’d not thought that having Calum as your lockscreen could actually annoy Luke, but you’d change it and neither of you would say another word.
Ashton:
Michael being Michael, he’d steal your phone and change your lockscreen to him, making you prmise not to change ti back. Ashton wouldn’t be present to witness this, so when he’d see your new image as he’d unlock your phone to play some stupid game,. he’d actually be quite hurt. You’d be sat next to him and see his face change so you’d ask him what’s wrong, to which he’d mumble something about a “picture of my best friend you find sexy” being your lockscreen, making your laugh as you explain what Michael had done. Ashton would still be confused, wondering why your phone revolved around your boyfriend’s best friend, but he’d just change the photo to a picture of you and him, knowing Michael would kill you when he’d find out.
Calum:
He’d not think much to the weird friendship you and Ashton would have going off and how open you’d be with one another, though sometimes he’d not understand it as much as he’d like to. You’d wake up next to him and head off the the bathroom before your alarm would go off, but Calum would still be there and he’d reach over to turn the alarm off. As he’d do so, he’d see a picture of Ashton as your lock screen and he’d laugh at first, thinking of when the photo was took and how Ashton sent it to you to make you laugh because you’d missed them all so much on tour. But after a while, he’d wonder why you’d changed it from that selfie of you and him. When you’d come out of the bathroom, he’d casually just ask why Ash was your wallpaper, to which you’d laugh and actually admit you’d have no idea and you’d change it back without Calum noticing, just because you’d not want him to think of anything bad between you and Ashton.
Michael:
Michael knew you’d be a secret fangirl and he’d actually find it quite entertaining as he’d catch you reading fanfiction and reblogging pictures of the band on Tumblr when you’d least expect him to be around. But he;d not actually know of your “celebrity” crush on Luke, so seeing you have a picture of Luke on stage as your lockscreen would confuse the Hell out of him. Fair enough, you two wouldn’t be “exclusive” or anything,but t’d be a bit weird for him to see a picture of one of his best friends as the girl he’s seeing’s lock screen every time you’d open it and answer a text or whatever. Michael would actually be sneaky about it and he’d wait for you to enter your phone password in front of his eyes just so he could memorise it, and at the first opportunity that you’d leave your phone unattended, he’d unlock it,. take a selfie of himself that would be really weird, and he’d set that as your lock screen. Your reaction would be priceless when you’d see the new image and there’d be no doubt of you keeping this long for as long as possible.