What I tend to do it for certain really important scrolling tiles that need to look seamless..is to put a very small fade out gradient on one edge of the Seamless tile..but also allowing for the extra fade out...of course...much like the sprite "bleeds" for plants and flowers etc...by doing this you can overlap your tiles just enough and the "Gap" is not seen if you do your art asset correctly...nearly every professional company uses this "Edge Bleed" technique..its very clean and fixes so many problems .......also MeJustMe..In regard to your Sand dune sprite issue this technique works as well.....Use an Alpha blended bleed edge on all your necessary Parallax Sprites...This way Overlap is not seen at all.....and to get variation in your Parallax dunes...Make 4 or 5 sprites in such a way that they can be blended and randomized..Art Asset creation is as important to your game final design as every other part...so spend some time..figuring out a lego block approach to all of your parallax sprites just as you would for your...normal level sprites......
What I mean is....This layout
(which is only a teeny part of the Enormous layout) made up entirely of only These parts
and a few extra Parallax Backgrounds & FX
So as long as you alpha blend the edges you can do amazing stuff because everything blends into every thing else...Good asset creation is an Artform in itself...Practice makes perfect..
If you are clever with your scene object design you can build entire world from only a few props..like the creative team did in the "300" movie..They only made 1 scene ROCK prop and just shot it again and again from about 30 different angles...very simple idea...same principle here mystazsea2012-11-05 16:42:33
When in doubt..or you are lost in a Zombie apocalypse or someone is giving you a hard time..Remember one thing..... Read the Construct 2 Manual..it will save your life.:)