To display images from a SharePoint in Power apps, We need to follow these below steps:

Create a Document Library in SharePoint Site 

Create a Canvas app in PowerApps

Add a Gallery to your App

Connect a new Data Source and SharePoint Site to your App

Create a Document Library in SharePoint Site by using form in power apps when we given will display in sharePoint

 

When we submit data in form it will save in sharepoint and it will display in gallery

Create a Canvas app in PowerApps

Open the Power Apps page through the Browser Make.powerapps.com Sign in your Power using Microsoft account

In the Power Apps page, Select + New app -> Canvas as shown below.

 

Choose Tablet layout under the Blank app section.

 

Add a Gallery to PowerApps App

In the Power Apps Canvas App, Select Insert -> Layout -> Vertical layout as below screenshot.

Connect a new Data Source and SharePoint Site to your App

Expand Connectors and select the new Data Source as SharePoint as shown below. Also, you can directly search the SharePoint in the Search bar.

Provide your SharePoint Site URL for the location of your list and hit the Connect button. Also, you can directly specify the SharePoint Site Url under the Resent sites section.

Choose a Sharepoint list or SharePoint Document Library (Image for power apps) and click on the Connect button.

Now you can see the gallery screen will appear like this below screenshot. That means, no images will appear until we bind it to the images Data Source.

Select the Gallery screen and go to the Properties section. Change the Layout as Image and title as shown below.

If you will preview or publish the Power Apps, you can see the output like below: