Yes, indeed. Very easily.
All you need to do is make the transcriptions similar enough so BG thinks they are duplicates, and then you can merge them.
Suppose one record is for R G Smith, 1855-1932, and the other is Ralph Gordon Smith, with no dates at all, but you know they are actually two sides of the same headstone. That's probably not enough to make BG realise they're duplicates. To make them duplicates, just edit Ralph's record and put some dates on it, and then edit R G Smith's records and flesh out his name to Ralph Gordon. Refresh the pages, and they should now both have a Duplicates (1) button in the top right corner, next to the Edit button. You then merge one into the other. Both records, and both photos, will now appear under the one grave listing.
Suppose one record is for Ralph, the other record is for his wife Mavis, but you know they are two faces of the same monument. You can't merge them as they are, and you can't tweak Ralph's record to make him look like Mavis, or vice versa, because they're not the same person. What you should do instead is go into one record (let's say Ralph's), click on Edit, then Add Missing Individual, then use the blue person icon to open up a new set of transcription fields, and create Mavis's record. Give her the same name and same dates as on her own record. You now have a duplicate for Mavis, which should say Duplicates (1) in the top right corner, same as in the example above. You can now merge the duplicate records for Mavis, and you'll end up with a single grave, containing two photos, and two records - one for Ralph, one for Mavis.
If these two examples don't cover your specific situation, and you need more help with it, let me know the URLs and I'll have a look at them. You can either post them here, or email me privately (I assume you still have my email address?)
A tip about merging: in theory it doesn't matter which record you merge into which. In practice, be careful if one has something in the Personal History section, because there's a bug in the Merge function that will make it impossible to alter the Personal History after merging. (I have reported it to BG, but last I saw, it hadn't been fixed yet.) My practice is this: if record A contains even slightly more "Other" information than record B (by "Other", I mean Personal History, Military History, Others Not Buried Here, Relationships, etc - basically anything which isn't the vital name, date, etc info), I strip B's record of whatever Other info it does have, transfer it to A's record if it isn't there already, and then merge B into A, so at the end of the merge I'm left with A's record containing the full information.
Good luck. Let me know how it goes.