Composition of images with different dimensions

Question

I created a code to make an image composition ...

back=Import["https://i.stack.imgur.com/ouBUD.png"];
img1=Import["https://i.stack.imgur.com/0o8UW.png"];
img2=Import["https://i.stack.imgur.com/uHQWP.png"];
Graphics[{Inset[back,{Center,Center}],Inset[img1,{Left,Bottom}],Inset[img2,{Right,Top}]}]

I tested the dimensions to confirm that this composition is possible:

ImageDimensions[back]
ImageDimensions[img1]
ImageDimensions[img2]

I'm trying to generate the image below:

What is missing from the code so I can get what I want?

Answer 1

Need to specify positions for Inset in a specific way.

Graphics[{Inset[back, {Center, Center}, {Center, Center}, ImageDimensions[back]],
  Inset[img1, Scaled[{0, 0}]],
  Inset[img2, Scaled[{1, 1}]]}]

Answer 2

Perhaps ImageCompose?

Fold[ImageCompose[#, #2[[1]], #2[[2]], #2[[2]]] &, 
  back, {{img1, {Left, Bottom}}, {img2, {Right, Top}}}]

If you wish to have a Graphics object, just wrap with Show:

Show[%, ImageSize -> 600, Frame -> True, PlotRangePadding -> Scaled[.02]]