Quickpic is designed to be a replacement for the standard Android gallery. Which is good because I find the standard gallery at times a little slow, sometimes a little buggy and sometimes just unusable. Quickpic can also set wallpaper for you, which I find the standard gallery quite often gets wrong.
Quickpic is free and available in the Android Market. Once installed you open the app up and it scans your device for images and videos. This would normally take the standard gallery a while as it seems to reload every time you open it up, with Quickpic it is done in seconds, it also caches the thumbnails as well to improve future load times. It will find pictures you did not know even existed. At first this view may be a bit cluttered with music album art, but if you want to exclude an album you just long press on the folder and choose exclude. There are a few settings as well to allow you to further customise the view. For instance you can manage included and excluded folders, you can set it to open in the last viewed folder, you can password protect hidden folders and you can change slideshow settings. The standard Android gallery does not have any settings at all. Also tap the icon in the top left and you get a detailed list view instead. Below are a few screenshots of the app in action.
Once you have chosen a picture to view you can upload it, view detailed info about it such as resolution or set it as a wallpaper. Android in general seems to mess up wallpapers, I find if you use the standard wallpaper app it will crop a section from the middle of an image that will be then enlarged to fit the screen. Quickpic takes into consideration the resolution of the screen and checks whether or not scrollable wallpaper is disabled. This means you can set wallpaper how you imagine it should work. Below are some more screenshots of it setting a wallpaper.
Quickpic is a great app, that in my opinion plugs a hole in Android, where previously it did not work a 100 percent. Being able to override the defaults for the camera, image sharing and wallpapers makes this a great replacement for the standard gallery. Below is a link to Quickpic in the Android Market.