With Astah, you can add images which are associated with models stereotype. For example, when you want to show Database icon on UseCase diagram, this is how you do so.
(1) Have an image file to represent a database ready.
(2) Open .asta file, select a root package in the tree structure, and then go to [Profile Stereotype] tab in the pane below. Click [Add] button.
(3) A stereotype will be added, click [Edit] button
(4) Another dialog appears. In the stereotype field, enter a stereotype in it and then click [Icon] button and specify the image file you want to associate with model which has this stereotype. In this example, I type “database” and upload an image of database.
(5) Create a model and add a stereotype, database
(6) At last, right-click on the model in a diagram and select [Icon Notation] – [Customized Icon] from its Pop-up menu.
Then the model will turn into the image uploaded!
Give it a try!