I have a requirement to display customer logo in SSRS reports (during development time we don't know what could be the customer logo). So, I have created a image control inside the reports with image properties as load from "External" and in the value I have provided the path to the folder within SSRS say "Images" and hardcoded the image file name as "CustomerLogo.jpg". Now when I deploy the reports to customer site, I just need to ask the customer to upload their logo inside the Images folder with the name CustomerLogo.jpg to show the logo dynamically, but the image is not getting displayed. Below is my code to show image.
Try below steps: Create a folder on Report Manager, i.e. Images. Grant the Unattended Execution Account the Browser role on that folder. Upload images to the folder. Edit the report in Visual Studio, set the image to External and the "Use this image" to "/Images/myimage.png" (without quotes). Deploy. The image should display in the report. actually a thing to note is the path can be either relative to your current path or absolute. Ensure you have the / in front of it if your report is in a separate subfolder from root
Link for reference https://www.sqlservercentral.com/forums/topic/issue-displaying-external-image