Thought I would add a nice image but then I get this... using the newest build
Enchiridion 1.9.4 3.1.5
Forge 1957

I tried an older build and still got it
using a png and a jpg both fail to show up.
not sure if its just not available just yet.
I tried with just progression and Enchiridion and still fail

Modpack List(so far)
http://pastebin.com/mQwv1pa8

Images work just fine for me, only thing looking back at code, what's your OS?
(Your link doesn't work btw)

Link does work... I had to copy and paste it in a new tab... its strange...
and I am using
Win10x64

Hmm, not what I thought it was then, I'll have to investigate later.

Well I can tell you trying out the Infitech 2 which uses the 1.7.10 version of yours does work for me, butyeah I'll look back later on to see what you have to say... going to 'try' and see if its something on my end but so far nothing, granted can't honestly think of anything XD... tried different settings in your config but nothing seems relevant... turned on the one for image sync but yeah...

Out of interest, the missing texture should end up getting printed to the log when it fails to load it, Can I get a copy of the log? Not that, that will help me much.

It's probably failing to load the resource pack. Somehow or something.

(The way images are loaded in the 1.7 version and the way they are in the 1.8/1.9 version is different)

Actually it will be better if you can: Use this debug version, load up the game, then try to insert some images then send me the full log. https://dl.dropboxusercontent.com/u/105284170/ShareX/2016/06/Enchiridion-1.9.4-3.1.5-debug.jar

OH MY GOD... my pc named the file wrong, I just analyzed the Log and it says the image is a 'Name..png' putting in 2 dots. how... the simplest stupid thing... isn't that always the way it is...
As my first time looking at this mod...

one possible request:

I notice when I clicked on 'enable scroll the book doesn't like scretch out to fit the whole page and the background image(loving the things I am finding out :)) it also is the same issue... I can't put in like a 2 times higher image so the page and background move together... image is static

Showing the splitting(image in background is just an test image):
2nd image is me figuring out goofup:

Ok person uses image of higher size for background: I also can't revert it back to default background in case I choose to?

Pro Tip: Don't try to open a .jar file to search for an image in game... while adjusting background... crashes game cause it 'Trys to use the .jar as an image' ... um... possible change stopping it from trying to pull up an invalid type?

Hehe. Always the silly things. I'm finding it kind of hard to follow what you're saying. Probably because it's late. But I think you're requesting the following things:

• A way to reset the background to default (without, editing json) (probably just a shift clicking the button?)
• I think you're asking for the option to make the background scroll as well, when scrolling is enabled?
• The background is a fixed default size, but you can edit that in the json, I doubt I'll add an ingame way for that
• As for the pro tip, not sure why you would do that anyway :P

its early didn't have coffee... was thinking shortcut... fail XD
Yes to first 2... didn't see 'size changing in json but will look but yes I would like to see a scrolling background which would make the book look neater/cleaner and make us think your even cooler than you already are :)

hope didn't stroke your ego too hard there... your one of my top 3 favorite mod designer currently :)