What I'm trying to do is to paste some images from my app in SMS.
UIPasteboard *pasteboard = [UIPasteboard generalPasteboard];
NSString *imagefile = [[NSBundle mainBundle]
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:imagefile];
UIImage *ui = [[UIImage alloc] initWithContentsOfFile:imagefile];
pasteboard.image = ui;
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"sms:"]];
"Paste" action will be shown only if the paste board contains the supported item for the current object(here Text Field) you tapped. It seems that you are adding only an image to the paste board. Text Field doesn't support images. So "Paste" action doesn't show up.