> If you can decide on what client interface you want to use there should be existing resources on the web walking through how to do this using that client interface.
Something like this:
INSERT INTO images(image) VALES( loadfile( /home/igor/my_image) );
Looking to run it from gAdmin in the Terminal.
As SQL is executed on the server there is the major issue of the server being unable to resolve /home on the client machine. But maybe pgAdmin has its own way to deal with this. Have you read its documentation?