Ok, I have spent the past few hours working on the Maxx's _cli .ski and .dat files. They are different than the V3x and V3xx ones, as the screen is bigger and there are more .gif's (37 to be exact).

Here is what I have so far, some info on the 37 .gif's included in the .dat file:

001.gif - 120x24 - Header Background in menus
002.gif - 5x5 - top corner of scroll bar background when in music
003.gif - 5x1 - scroll bar background when in music
004.gif - 5x5 - bottom of scroll bar background when in music
005.gif - 5x5 - top corner of scroll bar background when song is playing and in ring styles. best to leave transparent
006.gif - 5x1 - scroll bar background when song is playing and in ring styles. best to leave transparent
007.gif - 5x5 - bottom of scroll bar background when song is playing and in ring styles. best to leave transparent
008.gif - 5x5 - top corner of scroll bar when in music
009.gif - 5x1 - scroll bar when in music
010.gif - 5x5 - bottom of scroll bar when in music
011.gif - 118x26 - header background on lock/unlock message
012.gif - 118x4 - message bacground on lock/unlock message
013.gif - 118x2 - message bottom on lock/unlock message
014.gif - 113x24 - selected background in music menu
015.gif - 116x74 - not sure
016.gif - 114x49 - not sure
017.gif - 12x12 - right arrow unpressed
018.gif - 12x12 - left arrow unpressed
019.gif - 12x12 - minus sign (down?) unpressed
020.gif - 12x12 - plus sign (up?) unpressed
021.gif - 12x12 - right arrow pressed
022.gif - 12x12 - left arrow pressed
023.gif - 12x12 - minus sign pressed
024.gif - 12x12 - plus sign pressed
025.gif - 12x12 - menu button unpressed
026.gif - 12x12 - menu button pressed
027.gif - 124x21 - not sure, looks like 11
028.gif - 124x62 - not sure, looks like full window version of 012
029.gif - 124x9 - not sure, looks like top of 016
030.gif - 111x18 - not sure, looks like 14 but a little shorter
031.gif - 124x8 - not sure, similar to 029
032.gif - 80x80 - looks like a volume background, although i can't find where its used
033.gif - 94x18 - not sure, looks unused
034.gif - 94x18 - not sure, looks unused
035.gif - 120x24 - not sure, looks like 001 but lighter
036.gif - 120x24 - options background when playing a song
037.gif - 120x24 - looks same as 036

If anyone has any more info on those, post it here. I am also working on my first .ski and .dat for the outer screen on the Maxx. I'll let you guys know when I'm done, tonight or tomorrow

thanks to poetic_folly for the original guide.