I *still* can't get rid of the caption gradient that became default in 1.5.
Set both captionBackColor and captionBackTopColor (in JuiceboxBuilder-Pro's 'Customize -> Color' section) to exactly the same values (color and opacity).
captionBackTopColor has different default values for Large Screen Mode (rgba(0,0,0,0)) and Small Screen Mode (rgba(0,0,0,0.3)) so if you do not change captionBackTopColor in JuiceboxBuilder-Pro's interface, a captionBackTopColor value will not be written to the gallery's configuration file and the two default values will be used.
If you want to ensure that a single captionBackTopColor is used in both screen modes, change its color or opacity slightly from its default value. Then, to remove the gradient, set captionTopColor to exactly the same color and opacity as you've used for captionBackTopColor.
images showing my Color settings in the Juicebox Pro app (which are unclear, I can't even tell what some of them change)
Click on the small color box next to each color option and you'll see the exact hexadecimal color code that corresponds to the chosen color.
the demo appearance in the Juicebox app
Unfortunately, the integrated browser which comes bundled within JuiceboxBuilder-Pro does not support certain CSS3 properties (such as gradients and shadows) so the live preview will not be 100% accurate.
This is a known issue and is noted as such in the JuiceboxBuilder-Pro User Guide. Please view the gallery in a browser for a more accurate preview.
I was also wondering if it's possible to change the position for the next and last image arrow buttons. 1.5 changed them to be on top of the image rather than off, to the side.
Set imageNavPosition ('Customize -> Main Image') to STAGE rather that its default value of IMAGE. The main image navigation arrows will then be positioned relative to the stage rather than the images. However, please bear in mind that if the images take up a lot of the gallery's image area (which will depend on the gallery, image and browser window sizes), the navigation arrows may still be overlaid on top of the images. If this is the case, then you might like to compensate for it by increasing the imagePadding ('Customize -> Main Image').