If the sticker isn't showing the person's profile picture for you, that's a Telegram limitation for bots, it simply means they haven't started the bot, they've blocked the bot, or they've just disabled the bot from seeing their picture in their privacy settings.
To combat this, all users who it can't see the profile picture for will now have the coloured avatar like people who don't have a profile picture do on your app
The background of generated stickers is also now the dark blue you see on default dark mode clients