Great, thanks eishiya... I actually read about this in the manual for Deluxe Paint, but sometimes it's hard to transfer the theory to practice... so your feedback (and the feedback of Hapiel on the forum too) is very valuable. 

Re: hue, there's some art terminology that'll be helpful to know:

- Colour is the combination of hue, value, and saturation.
- Hue is the redness, blueness, pinkness, etc of a colour. It's what you meant when you said "colour", but it's best to use the art terms so that we're all on the same page. When an artist hears "change the colour", they might think you want to change the value and saturation too xP
- Value is how light/dark a colour is.
- Saturation is how intense a colour is. Low saturation means greyish, high saturation means bright and intense (e.g. neon).

Here's an image briefly illustrating these concepts.

So, yes, you understood me correctly :D
Also, the new preview looks good!

 Okay I have redone my preview images, thanks ! :)

Thank you for your feedback, much appreciated, and all taken on board.

Changing hue is like changing the actual colour right, as opposed to the just the "darkness" as I am currently doing?

I wasn't sure how to produce the preview photo I must admit... maybe next time a small extract would be better :)

It's best not to auto-scale at all, even with nearest neighbor resampling. The results aren't hand-made pixel art, and undersell the artwork because they distort it.

I quite like this piece. Nice sense of scale on the layers, even though the buildings get larger. I think it would benefit from more hue variation though, it feels a bit dull despite the pretty pinks.

Probably 1041uuu lol.

You should remove the antialiasing from your preview photo!! You should either crop out a 100x100 snippet from your image or use the nearest neighbor algorithm when shrinking the image.