XFLI is based on Hires FLI and a low-priority multicolor sprite-layer, resulting in a 192×168 pixels screen of faked hires, (since the sprite-layer is still in multicolor). Further there is the possibility to add one sprite-color split every 2:nd line (correct if wrong) to gain more colorfullness. This gfx mode falls in somewhere between UFLI and MUFLI i would say. The introduction of sprite-color splits makes it no longer possible to purely divide the picture into graphics and code, since part of the picture is actually stored within the code.
Checkout XFLI here: Digital Magic / Crest. Here are also more versions of XFLI, like full screen hight, interlace and avoiding FLI-bug.