Unfortunately there is no way afaik to mass export+import wiki media files. However, I can automate much of the image importation using a script so manual importing is not needed.
I was manually importing a few, but wasn't sure about what licensing they should have?
Also, how do you go about writing scripts to interface with this wiki?
All images from the game (regardless of type) are always used under fair use as they are copyright of Jagex Ltd.
About the licensing issue, I've found the upload box inadequate for adding license information. The RS wiki already has a series of templates for license information which were imported to this wiki. They have the form:
{{Image_type license|Subject}}
For example:
{{Inventory license|Bronze dagger}}
for the bronze dagger inventory picture
If you're not sure what the template is for the kind of image you're uploading, then check with the RS Wiki to see if they already have that kind of template
Every image you take from the game is literally going to use the 'fair use' license (if didn't, we couldn't use it on here). I.e. one can use {{Fairuse}} for every image just fine. The {{Inventory license}} template and all the other various types are simply a fancy version of the fairuse template that says it came from a video game and it's a picture of an inventory item or something along those lines. That being said, we should use those templates instead of the generic fairuse one, but not because it's inadequate (since it is), but since using those template automatically categorizes the images. For example, the Inventory license template adds image to the 'Item inventory images' category IIRC.