Dear Rachel,
To be able to upload bigger pictures you have to change a little thing on the "options.php" file from your indexhibit. You will find this file inside "ndxzsite" folder and then inside "config" folder. You can change there image quality and image size:
// image quality
$default['img_quality'] = 90;
$default['systhumb'] = 150;
// images max size kilobytes
// be careful with shared hosting
$default['maxsize'] = 2000;
I just changed image size and it works out fine for me. I just put 2000kb instead of the default one that it was 200kb if I remember well. I didn't change image quality. Then you can prepare your pictures in the size that suits better for you.
I hope this hopes to solve your problem. Let me know!!
NoemÃ.