Use Anything as a Legend
Create legends using anything, including tables, text, images, and graphics.
text = Style["legend", FontFamily -> "Arial", 25, GrayLevel[0.3]];
graphics = Graphics[Table[{Hue[i / 2π], Opacity[0.5], Disk[{Sin[i], Cos[i]}, 0.5]}, {i, 0, 2π, π / 6}], ImageSize -> 50];
table = Grid[Array[Subscript[a, ##]&, {3, 2}], Frame -> All, FrameStyle -> Gray];
graphics3d = Graphics3D[Sphere[], ImageSize -> 65];
image = ImageCrop[ImageResize[ExampleData[{"TestImage", "Splash"}], 70], 60];
control = VerticalSlider[ImageSize -> Small];
plot = Histogram[Table[RandomReal[{0, 10}]Sin[x], {x, 0, 2π, 0.05}], BarOrigin -> Left, AspectRatio -> 2, ImageSize -> 60, Axes -> {False, True}, Ticks -> None];
formula = HoldForm[Integrate[x ^ x, {x, 0, Infinity}]];Grid[{{Plot[Sin[x], {x, 0, 2π}, PlotLegends -> text], Plot[Sin[x], {x, 0, 2π}, PlotLegends -> graphics]}, {Plot[Sin[x], {x, 0, 2π}, PlotLegends -> image], Plot[Sin[x], {x, 0, 2π}, PlotLegends -> formula]}, {Plot[Sin[x], {x, 0, 2π}, PlotLegends -> table], Plot[Sin[x], {x, 0, 2π}, PlotLegends -> plot]}, {Plot[Sin[x], {x, 0, 2π}, PlotLegends -> graphics3d], Plot[Sin[x], {x, 0, 2π}, PlotLegends -> control]}}, Frame -> All, FrameStyle -> Gray]