I'm not seeing any slowdown on my desktop.

I've got a simplified classic scheme however. Perhaps try looking into desktop effects and theme features like menu animations. Toggle any features off and see if one of them causes it.

PS:
Oh, it might also be something to do with the individual images. Presumably the two actual menus aren't both using the same three images, and they definitely aren't using the random image I grabbed for the task.

PPS:
You can embed an image in your source, for example:

#Embedding GIF bytes:
my $icon = pack('C*' ,71,73,70,56,57,97,64,...(Many more bytes)...,0,5
+9);
my $img = Tkx::image_create_photo(-data => $icon);
$mw->g_wm_iconphoto($img);
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