can you post IMAGES that are small, or does it have to be links? like under a spoiler?

I'm not 100% sure if it's what you're asking, but here is the official rule about image size limits: https://subeta.net/help/rules.php?act=rule&id=29

for example, i just saw in a thread in the art forum this:

spoiler 450x325 450x325 450x325 spoiler 450x325 450x325 450x325

I post sample images under a spoiler in the first post of my thread without any issues. According to the rules the images you post should be no larger than 325px height by 450px width. The forums will automatically resize them to around 350px high if they're any larger.

You probably want to be selective about your samples and not post so many that you make the thread load slowly or eat up a ton of mobile data for viewers.

It might be kinda bad to say it, but image size enforcement is kind of lax. Be considerate of your audience that might have a slow connection or limited data. Don't post obnoxious amounts of images or huge images, link to your website/tumblr/DA/whatever for bigger stuff, and you probably will give no reason for anyone to complain about your thread.