use File::Spec::Functions;
opendir (my $dh, $dir);
@img = map { catfile($dir,$_) } grep /\.(jpe?g|gif|png|bmp)$/i, readdir $dh;
closedir $dh;


use Path::Tiny 'path';
@img = path( $dir )->children( qr/\.(jpe?g|gif|png|bmp)$/i );


use File::Find;
find(sub {
  push @img, $File::Find::name if /\.(jpe?g|gif|png|bmp)$/i
  && $dir eq $File::Find::dir
}, $dir);

##</code><code>##

find(sub {
  push @img, $File::Find::name if /\.(jpe?g|gif|png|bmp)$/i
}, $dir);