I'm not seeing the image in your post. Can you try uploading it again? 

I’m having trouble uploading, so I’ll just share the link:

http://www.samizdat.qc.ca/arts/lit/PDFs/VoyageoftheDawnTreader_CSL.pdf

The picture is on page 83. There’s actually also some illustrations at the end of the last two chapters.

I would perhaps assume, given that the publisher of that PDF is doing so under a claim of Public Domain in Canada, that there must have been an extant copyright or trademark issue preventing them from using the original Pauline Baynes illustration... Therefore since they appear to be very keen to emphasize how above-board their republication of the text is with respect to Canadian Copyright law, but say nothing of the images, I would perhaps assume they are the copyright holders themselves for those images - i.e because they created them their selves.

Pure guesswork, but that's what I'd assume.

@icarus
In my experience of ebooks (5 years of Kindle), there are almost no pictures at all.

It is true that Narnia is out of copyright in Canada [this prevented the Estate stopping an awful stage production in the Niagara area, with a female Aslan among other abhominations]. I believe that the Estate did write to them about it, but couldn't force their hand.

The introduction suggests an earnest Canadian keeping up the national ethic of politeness and graciousness. 

I've got the Chronicles from Canada as well, I downloaded them as PDF files. In mine there are no interior illustrations because of copyright issues. But the Baynes  illustrations on the covers are there.