Used this source image:

Used GMIC Engrave (default values) asking to create a new layer.
Used GIMP GEGL Mosaic (default values) on the background (original).
Set Engrave layer mode to Multiply.
Created a new layer from visible and set Mode to Screen.
Got this Outcome, which I like as combined effect.

If you like it too, repeat my steps.

If someone follows these steps, (s)he should get a Gimp image made of 3 layers:
Bottom layer

Intermediate layer

Top layer

If you set this layer to Screen mode, you get the outcome shown on previous post.

Thank you so much Dinasset for this nice tutorial. I love the result and I'm going to try it. (I've been busy with other issues)

OK, Diego; I'm game. Used G'MIC Engrave followed by G'MIC Segmentation and blended that back with the original and then some cleanup work.

Good! Now two plays instead of one.

Good result Lyle, but it's a bit different or it's my eyes?
Well this is my first result but I'll do more on a larger picture. Thank you Dinasset.
(I didn't see GEGL Mosaic, where it is? )

My second try.

OK, Diego. Using G'MIC Local Orientation and G'MIC Metallic look presets and blending them together along with Gradient mapping (Metal Gradient), I got this glassy ice look.

Another nice result Lyle. Sorry, I misunderstood what to do. Thanks a lot for sharing your results.

Issa, Lyle is suggesting "different" simple tries (not trying to follow "my" way), so there are now 3 for experimenting.

Tried Lyle's first tip, applied PinLight mode on the layer "manipulated" thru Engrave+Segmentation , got a very nice (IMO) watercolour effect

Issabella, your tries on "my" tip are nice, thanks.

Another simple play: use GMIC SuperPixel with random colours creating a new layer, set mode to GrainMerge:

This is the outcome if you set the mode to Divide

Taking Lyle's suggestion on using Local Orientation (only that), setting channels to YCbCr Luminance I got an outcome which may go into OMG Collections

Like the pressed tin look, Diego.

I did my simple experimentation, too.
My steps were: Gmic _ Edges (at a new layer) _ Gimp Colours _ Invert and set the layer at screen _ New from visible _
and applied Invert again on the upper layer.

Thanks Issa, nice play.
So far, only you and Lyle attempted to create/follow quick and easy but interesting flows.
Let's see who is next...

Enhanced details via convolution (dupped, ran G'MIC Bilateral smoothing filter on top layer and set that layer to Grain Extract) and duplicated the convolution layer until happy. I then ran G'MIC Anisotrophic filter (fake smudge) on the result. I dupped and ran Rodillious (thin and small) for added glow. Had to recolorize (set to hue) with original image due to convolution layer step.

Another simple way to increase color "density" in an image:
duplicate the layer
add transparency
apply color-to-alpha (white)

Example:
original

modified