To get an image link I usually upload my battle map with tokens using Post Images. com which used to work fine, but now they are being marked as Spam and cannot be posted. Why is it being marked as spam? How else can I post custom battle maps on forums for my players. 

Also why is copy and pasting not an option?

As for spam, I cannot say.

As for posting images, see guide: https://www.dndbeyond.com/forums/d-d-beyond-general/general-discussion/193584-how-to-post-images-in-forum-posts-and-pms-here-on

I understand how to post images, but I am not using images from a site. The map is on my PC which I then need to create a link for it using websites like Post images.com. 

The guide explains how to upload an image from your PC into a hosting service and then use the link to it here.

Postimages.com is down and not working right now. The guide tells you how to use an alternative.

Quote from Arenlor >>

I would recommend using Imgur. However I did mark them as non-spam fairly quickly. In the future if one gets caught as spam please feel free to post and ask us to look into it so we can mark it as non-spam and let the system learn.

 Imgur works, but people have to get the right link from the BBCode link and remove the [IMG] tags.

I would be so much nicer if there a way to link and have it interpret the link.