Hey there, this is probably pretty elementary but: Does textadventures.co.uk support images in games (specifically JPEG) made on Quest Lite? Do I just have to upload the asl file?

If you just uploaded the ASL there wouldn't be any images. You need to upload a ZIP file containing both the ASL file and your images. Alternatively if you upgrade to Quest Pro you can create a CAS file including images, then just upload that.