I am assuming most of the images you have, have a white background.
I think Inkscape is more of a vector program and you may find it easier with a free photo editing program called GIMP. You can of course get Photoshop Elements.
There are a couple of things you need to learn when creating a scene
1. Layers - this is where the program allows you to have each image or element in the scene on a new layer, so you can freely move it around without disrupting the other 'layers' in the scene.
2. Magic Wand tool - This is fabulous for removing the white background from 'outside' the lines. Simply select the tool, click into the white area and it should select an outline of the white, then hit delete. However, not all images will have perfectly closed lines and so you may find parts or the whole image will become transparent.
3. This is when you create a 'new layer' UNDER the image you made transparent and use the 'paint brush' tool to paint back in the white areas. By doing this on a new layer under the outline you wont make a mistake and go over the lines.
If you get images that already have a transparent background 'around' the opaque image then you can use a program as simple as MSWord to create a scene. There are a few more companies now supplying their images in this format so people can create scenes. I have a video
on how to use my images here in MS Word. Just look at the description when you are buying and see if they mention the image comes suitable for layering.
There is also a step by step guide
with images going through what I tried to explain above though using Photoshop Elements - GIMP is essentially the same but free.
I am going to see if I can make a video of how to use GIMP. Just a time factor.
Here is a link to GIMP
if it helps.
Hope this helps a little and you get hooked on scenes like me!