This is MMPlayer with the Zodiac skin playing a video. This skin supports landscape devices and will use available screen area.
And here's the gray skin playing video. This skin also supports landscape (and portrait) devices but is here shown in 320x320 mode.
This skin is designed to fit both a small video area and some sliders to control audio/video properties. However, if you want to fill the whole screen with video, just tap the video area to expand the video to full screen.
This is how the gray skin looks while playing audio. As you see, skins can show a different set of controls depending on the type of media currently playing.
This is a typical prefs form layout (from the Cobalt skin). This skin uses a separate form for most settings. However, this particular skin also has a volume slider on the main form.
This skin, on the other hand, has all the controls crammed into one form. It still leaves plenty of room for a large audio/video area.