I totally agree with you. Both topics are already named here in this board and on github. For further infos and discussion please use these topics.
Thumbnails
Board: [Feature Request] iOS App: image thumbnails
GitHub: Add thumbnails and grid view - ios #73
Multi Select
Board: [Feature Request] iOS App: multiple file selection and processing
GitHub: Perform action on multiple items at once (aka. multiselect) ios - ios #52