Here's a look at the new features:
Customization is one new feature: you can now personalize the wallpaper on your XMB with a photo. This was one of the top three requests we received via the blog’s contact form. When viewing a photo, simply bring up the options screen by pressing the triangle button and selecting “set as wallpaper” from the options displayed. Additionally, you can now change the order of the games displayed under the game icon on the XMB.Source: PlayStation
Another new feature focuses on added communication elements: When you’re sending messages to friends on PLAYSTATION Network, you can now use emoticons. We’ve added a bunch of emoticons that can be easily accessed from the virtual keyboard. Also, another cool addition is, when an avatar is displayed during voice/video chat, the avatar will move in response to audio.
Finally, on the more technical side, you can now play AVCHD videos saved on a Memory Stick or digital video camera, and we’ve added the ability to upscale audio CD output from your PS3. Now, there are two requirements for this feature: the device you’re outputting to must support a sampling frequency of 88.2 kHz or 176.4 kHz, and your PS3 must be connected to that device with an HDMI cable or digital optical cable.
Oh, and one more thing: you can now eject discs using your controller by selecting “Eject Disc” in the options menu after you push the PS button.
Several other minor options will be included in 1.90 including a few new display options that will allow you to adjust your display while playing PlayStation, PlayStation2 and Blu-ray movies. More info on these options as well as detailed info on the rest of the 1.90 additions will be available later this week. We’ll update this post with a link to that info when it’s available.