Normally you will be doing it thru an application written in say VB or PowerBuilder etc.
I have done this in PB and can tell u how it can be done thru that.
PB provides for blob (binary large object) variables. You can open a file and read its contents into such a variable. PB also provides an interface to ODBC drivers to send this data thru a special update statement called UPDATEBLOB
UPDATEBLOB table
set image_column = :blob_variable
Only requirement is that the ODBC connection should be set with autocommit = true mode
I have seen image control in VB, where you can define the image file path and the image control can be mapped to a datasource/data column. I guess, one should be able to insert/update using such a control in a VB app. Probably you will need to explore on this..
RT