Hi @Mammifero ,
Could you tell me:
- Do you store the image in the document library?
- Do you have a list? Does it have a hyperlink column? Just like the picture below.

If my assumption is correct, please try the steps below:
1\ Please make sure the link is correct. ‘EEDDCCBBAA’ is my document library.



// copy the link
2\ Create a list 'Employees list' and create a Hyperlink column. Save the copied link to the first record.

3\ Open the App and refresh the data source.

4\ Add an Image control and set its Image property to:
First('Employees list').GGG
5\ The result is as follows:

If you still cannot get the image, please check whether the user who uses the App(you) does not have the permission to access the image.
You could try :
1\ Add the user to the group
2\ Share this image directly


Best Regards,
Wearsky
If my post helps, then please consider Accept it as the solution to help others. Thanks.