Hello,
I've been wondering how to put image on the subject line? Little instruction will be appreciated or please direct me to the thread is someone already posted it and I'll lock this thread. Thank you bitcointalk community

you need to upload you desired image to an online image hosting like this
https://ctrlq.org/images/ then you must
copy your unique image link after you upload that image. and then post it here in this format
[img]your image link here[/img]
the image should show up after you've done this.