I have Pico CMS in my nextcloud, when inserting an image in the page it only shows the name of the image. how could i fix it
Did you try this? How To Add Images in Markdown | DigitalOcean
Check this thread
Can confirm, editing your .md files with the built-in markdown editor in Nextcloud does not seem to add pictures correctly. However, you can directly edit the .md file in any text editor locally on your computer. I use Atom for this, and open the synced folder in Atom as a project. You can just as easily use notepad to edit the file.
The proper syntax to use to add a picture:
![name of picture](%assets_url%/filename.png)