Disclaimer: I'm at work at the moment so I cannot test this, but I think that the following should work.
Since you're posting in the developer forum I'm assuming that you run a recent nightly build of XBMC. The recent nightly builds include the new settings system which I base my answer on. I also assume that you are able compile OpenELEC by yourself because the file you need to create (in case it does not exist) is most likely part of the read-only file system of OpenELEC.
I'm not familiar with the OpenELEC build process, but the idea is that you (if it does not exist) create the appliance.xml file. This should go into the same directory as where you find for example the settings.xml file (in the xbmc source tree in
xbmc/system/settings/.
If the file does not exist yet, then create it and put in the following:
Code:
<?xml version="1.0" encoding="utf-8" ?>
<settings>
<section id="pictures" label="1" help="">
<category id="slideshow" label="108" help="">
<group id="1">
<setting id="slideshow.staytime" type="integer" label="12378" help="">
<level>0</level>
<default>5</default>
<constraints>
<minimum>1</minimum>
<step>1</step>
<maximum>600</maximum>
<formatlabel>14045</formatlabel>
</constraints>
<control type="spinner" format="string" />
</setting>
<setting id="slideshow.displayeffects" type="boolean" label="12379" help="">
<level>0</level>
<default>true</default>
</setting>
<setting id="slideshow.shuffle" type="boolean" label="13319" help="">
<level>2</level>
<default>false</default>
</setting>
</group>
</category>
</section>
</settings>
The important part is <maximum>600</maximum>, in settings.xml this is set to 100. By using the appliance.xml this should override what is in settings.xml.
The big question is of course whether or not the OpenELEC build system also stores the appliance.xml file in the read-only filesystem, or if it simply ignores the file.
Alternatively, you may be able to just edit the guisettings.xml file in your userdata directory and set the staytime to 600. However, I'm not sure if XBMC verifies the value when reading this file and if XBMC writes this file on exit and possibly resets it back to 100.