I've tried localizing your plugin and realized it's not ready for localization, although you did use some localization ready code in your plugin.
Please add the following line to beginning of code:
load_plugin_textdomain('Easy_Instagram', false, basename( dirname( __FILE__ ) ) . '/lang' );
Add a lang folder and a POT file that contains all strings.
On top of that, 2 very important string you left out:
and posted #T#
which are always in English despite shortcode option to manally define 'by' string.
Looking forward to your update.
Beyond that, it's a great little plugin. I'm still running it on a test environment, so I don't know if you've taken care of performance issues I've read about. But if you did, it's very promising :) Thanks for developing it.