One really easy way to get illustrations is to use Google image search, looking for images that have copyrights compatible with reuse.
For instance, you could look at the First 1000 Words in Greek
thread for some images. And add more to the thread if you can, let's make it easy for people to create various materials.
ἐξίσταντο δὲ πάντες καὶ διηποροῦντο, ἄλλος πρὸς ἄλλον λέγοντες, τί θέλει τοῦτο εἶναι;