Why do you want PPC? I'm thinking 10.6.x on the last Intel mac with Snowleopard support would be an 'upgrade' to your usecase.
Btw. what I miss most is the glory days of OSX Preview. This thing, I could just throw at it whatever I wanted and it would handle it without choking. Nowadays I have to force quit that damn thing more than I use it, just because I load some largish PNG. As a student this thing was the absolute killer feature for my mac, because I could put together conclusion papers way faster and in much higher quality than anything possible on Windows. Rectangular Text snippets being vector scalable after pasting into Pages and images keeping their original quality was just a godsend [1].
Preview shouldn't be falling over ever, even if PNG is a fairly inefficient format for partial loading. File a bug at https://bugreporter.apple.com or with Feedback Assistant.
Btw. what I miss most is the glory days of OSX Preview. This thing, I could just throw at it whatever I wanted and it would handle it without choking. Nowadays I have to force quit that damn thing more than I use it, just because I load some largish PNG. As a student this thing was the absolute killer feature for my mac, because I could put together conclusion papers way faster and in much higher quality than anything possible on Windows. Rectangular Text snippets being vector scalable after pasting into Pages and images keeping their original quality was just a godsend [1].
[1] http://imgur.com/a/slstJ