There aren't really any "good" synonyms for "Look!" as an exclamation. "Behold!", "See!" and "Lo!" sound dramatic and archaic, and "Voila!" (nicked from French) is for pleasing and perhaps surprising results. Borrowed expressions such as "Voila!" and "Ecco!" can also sound pretentious. There are colloquial expressions such as "Check it out!" and "Take a gander at this!" but I wouldn't say they're close enough to be synonyms; their tone and situation is very specific. Just stay with "Look!" and you'll have no problems.

Hello Yljaha, You could use 'Hey!' (pronounced 'hay') and/or the character's name Best wishes Bob

You can also use "watch" instead of look. For example: #Look at her, she is dancing. #Watch, she is dancing.

I agree with Peachy. Although you could reconstruct the entire segment with something like: in the corner of his eye appeared the things they had left behind he shouted... That might be useful if you have used the word look too many times in the preceding paragraphs.