I have a mobile app with a series of task that users accomplish through several screens. User performs an action, taps on the bottom-right icon ">" and goes on with subsequent tasks.
It is best to have a CTA button called Finish or Done rather than Save an Submit icon.
"Your buttons should always say what they do. Avoid vague terms and, most especially, do not confuse the user by having a single button do two things!" from One button for two actions
I'd use a simpler icon - probably just a regular check icon. The main reason behind this would be that user is already through the process. The closing of the flow is something a user would expect. If that's not a case, then a success state after the submission would be advisable. Icons are supposed to be symbolic and atomic in nature. If someone has to stop and think about what this icon would do, you're losing the meaning of using an icon alltogether. Use just text instead.
PS: This is all I can provide as asking directly for an Icon is against the policy of this SE. Hope this was helpful.
I'd go with the simple (big) button rather than using some icons which are not yet fully tested and recognised globally (like canonic images), especially for the submit.
There are lots of icons which can be used for submitting, but I think none of them were / are completely tested with the users. In order to introduce a new icon, a thorough testing is required.
If you are planning to use just the icon, consider using text along with the icon.
For instance: We use the floppy icon for save, but nowadays we don't see a floppy (not sure about others, but I haven't seen it lately for last few years), but it is recognised universally.