You would need to make some alterations to the zip file you can download from the Sprintr before building the app installer package. But as this is default Mx, you would need to this everytime you generate a new zip/app package.
In the www\js\bundle.js you would need to change the return of this function to the desired feedback. Save, zip back up and build your app package.
The colors of the background and button can be changed within Sprintr, but beware this would affect the signin page as well.
Hi Dinesh, Yes it can be done by approaching following scenario :
Click on Project dashboard in your modeler => then click on Mobile Apps -> Under Theme tab, you can upload the image for Custom Error Screen.
For uploading image, you need to do some work around, design one custom page and convert to PNG and try to upload from here.
But make about the resolution of PNG, before uploading.