Any graphics you create yourself in a graphics program have to be saved in one format or another, and you've said you are saving yours as jpg.
Firstly, I'd recommend going back into your paint package and saving out as BMP if you don't need any transparency, or as a PNG if you do need transparency.
But to be honest, I think there's something else going on here, because JPEGs do work fine with Construct.
As for the points you marked out, I do a lot of 3D modelling in 3D Max, and the mainstay format for models is TGA, but when I first came to Construct, it became clear that TGAs didn't work well with Construct.
It was only mentioned just in case TGA was the format you were using.
The other point you marked refers to the options you are given when saving a graphics file.
Saving TGAs gives you the option to compress the texture when saving, and PNG gives you the option to save as interlaced.
Again these were mentioned just in case you were using either of those formats, which we now know isn't the case.
I still believe that it looks like the graphics card drivers.
I've had similar looking glitches when my drivers were out of date (for instance when I first bough MineCraft I had lines like that in-game), and updating the drivers was the only fix.