since this plugin is no longer in development, editing the plugin files seems like a decent way of fixing errors that have arisen due to wordpress updates.
here's what i did to fix the shuffle issue of snivo:
• go to plugin editor
• select 'simple nivo slider' from your list of plugins
• make sure you're editing 'simple-nivo-slider.php'
• navigate to line 222 where you will see...
for random order:
for reverse order:
and so-forth and so-on...