To understand how Landscape handles ordering photos in reports, it's important to understand that photos stored in geography in Landscape and collected with the mobile app are actually made up of two different things:
1) The photo point. This is a geographical point that is stored in a layer (often the Site Visits layer). Photo points (and most other geography in Landscape) have the following fields available to them to edit: Name; Description; Map Label, Map Item Type, Map Item Status, and Species. This field also stores the 'Created On' (date) field; External ID; Id; Last Modified By (user); Last Modified On (date); but these fields are not editable.
2) The photo(s) itself. Photos are contained within photo points. A photo point can contain as many photos as necessary. The fields available to edit within Photos are: Description; Taken On (date); Taken By; Direction (degrees); and Status. These fields can be set independent from photo point fields.
When you take a photo with the Landscape Mobile App and click 'Describe' you are adding a photo description. If you tap on the photo point later and begin editing the description or name that you see, you will be editing the photo POINT. You must click on the thumbnail to edit the photo attributes. More on editing photos and photo points here.
In a report's photo block, Landscape will always sort first by GEOGRAPHY (photo point) and then within that point by PHOTO. This means you must use photo point attributes to reorder photos taken at separate photo points in a report if needed.
By default, this will be ascending (alphabetical) photo point name, and then within that point by ascending (alphabetical) photo description. The Landscape Mobile App automatically names photo points in order for them to appear correctly in your report. Your first photo point, created when you take your first photo at a site visit, is called 'Photopoint 01'. Your second photo point will be called 'Photopoint 02', etc. The numbers are zero-padded (01, 02 instead of 1, 2) because the sort is alphabetical. If the numbers were not zero padded, then 'Photopoint 10' would appear after 'Photopoint 1'.
So, for example, say that you took three photos within Photopoint 01 and described them as '1', '2', and '3' (we'll ignore the suggestion to zero-pad numbers for now). You then took one photo at Photopoint 02 and labeled it '5', and then a photo at Photopoint 03 and label it '4'. The report will print the photos in the following order: '1', '2', '3', '5', '4' because it always looks at geography first, and therefore is ordering the photos by their parent photo points 01, 02, and 03, even though the photos are labeled in the other order. If you wanted the photos to be printed in the correct order with the default sort applied, you would need to rename Photopoints 02, and 03 to 03 and 02, respectively.
You can choose how to sort the geography and photos by changing the sort field in the photo content block and by changing the 'ascending' vs. 'descending' options. For example you may wish to order the points chronologically by 'Created On' date:
Using 'Sequence Number'
If you don't like hand labelling each photo 'Photo 1', 'Photo 2', etc...you can use the merge field [[@SequenceNumber:Items]] as a shortcut. This field will print the number in sequence of whatever you're repeating. 'Sequence Number' can be selected from the merge fields list under 'System Fields'.
So, for example, as the report prints photos, the following block will print 'Photo 1', 'Photo 2', 'Photo 3', etc...
Be aware that because of how this function works, the number assigned to each repeat will change based on how you are sorting the repeated block. In other words, if you apply this field and then delete a photo or re-sort the list, the number displayed under each photo will change as a result.