I want to display base 64 image in MIT App Inventor which is stored in FIRBASE REALTIME DATABASE

[TIMAI2]

You can use the first extension here to display the base64 in an image component:

Base64 Tools - five little ones ;)

These three simple individual extensions are already rolled into Juan's Base64 extension, but I believe it may be useful to some to have access to individual functions for specific needs.... There is now a fourth little one, not included in Juan's extension, for the Canvas ImageSprite. There is now a fifth one, for converting binary files to and from base64 Image To/From Base64 This extension has two functions, the first will convert whatever image is in an image component to a base64 string…

or as Marco has indicated you can use a webviewer to display the image: