I totally adore your header. One of your best graphics, I say.
A great way to cut out people would be to use the Lasso tool. (I'm not entirely sure what your method of cut is, but I totally recommend it. At first, I didn't like using the tool myself, but I found it just as good to use as long as I zoom in on the image of the person or object I'm cutting out. Then to make the cuts of a person or object look smooth, use the blur tool. Set the opacity at 20 - 25%. Have the brush small in size... like 15-20, then go over the outlining of the person/object.
I like your dramione banner too! For your coloring, there are a couple of ways to achieve good coloring.
A.) Have a colored layer (of the color selected somewhere from the base) over all the other layers/images. Set the layer mode to "Soft Light."
B.) When you finished a graphic and when you flatten the graphic, you can use either, curves, levels, or color balance to experiment with to add coloring to the entire graphic. I can go into finer detail - just message me.
Another thing about coloring, you should keep in mind is when there are different skin tones of either the same model or different models, try to make sure they match so that it gives the graphic a natural look. Curves or Color Balance are your go-to settings to help with that.
For blending, particularly blending stock images, aside from using layer modes or lowering the opacity of an image, I find that using the eraser tool with a big-sized (130+ pixels) soft brush and just erase areas of an image helps with a cleaner, smooth blending of multiple images.
I hope you found those tips helpful! I'm here if you want me to explain further or if you want help improve making graphics and/or learn gimp better in general.
Edited by Asphodelic, 29 June 2017 - 12:49 PM.