It’s a lot of tails posed just right to look like mouth tentacles. I actually got it from this website which has a ton of hero forge pose resources
I don't know how to do it personally, but this subreddit has a link to a page with dozens of poses and glitched out figures, which is what I used for it.
https://airtable.com/shr7nVLBuqMHefIcO/tbl8CYvxtptcwLXDO?filter_Visibility=SFW
It is odd considering other custom mini sites feature a octohead option. Not sure all the legalities there.
There is a link for an Octofolk that someone designed in the heroforge templates located here:
https://airtable.com/shr7nVLBuqMHefIcO/tbl8CYvxtptcwLXDO?filter_Visibility=SFW
Unfortunately if you change the pose all of the tails reset so its a limited option to create "a humanoid with a tentacle mouthed cephalopod head"
Use Photopea it's completely free and works identical to Photoshop just in a browser (I don't think it works on mobile).
As for not knowing how to use photoshop it takes a bit of practice to do the harder stuff but replacing a background is super simple, just erase the existing background, add the image you want as a background to the project, resize it to properly fit, and then set the image to the bottom layer.
If you wanna learn how to do cooler stuff just google search for what you wanna do and I can assure you that multiple tutorial videos and blogs will pop up that you can follow along with.
Lots of Booth pics... 40 of them, specifically, and then taking them into DaVinci Resolve (which is free), using some free-for-personal-use music (linked in video), and one of the Orion Nebula pics NASA shared from the Hubble telescope :)
Here's the link to her books if you want to check them out.
i use https://www.remove.bg/ to get rid of the backgrounds of the characters, then use an editing software that works just on a tab called Kapwing to put said characters onto a sort of canvas where i can then add background images, text, ETC.
If you hold the left or right arrow keys the model spins. To make the gif, I started recording my screen with OBS, then spun him all the way around and stopped the recording. I cropped the size of the video and trimmed the start/stop times with https://ezgif.com/