Hello,
I uninstalled the 2.5.1 and then installed the 2.5.2.
Then I reconfigured the HTML splash image via the settings page. I used the same code as I used in the old version. Everything was ok at a condition: I could not add an hyperlink to the image or the image disappeared, and a sort of hyperlinked code appeared at its place. I solved using the Include setting, pointing to an external HTML page.