That depends on the size of your photos and videos actually. The Mini 2 has a storage capacity of 32GB, minus a couple gigabytes for the operating system and player app.
Storage Estimates:
The size of graphics and videos can vary widely but as a rough estimate:
Images: If we assume an average image size of 2MB, you could fit about 700 images on the Mini
Videos: If we figure an average size of 100MB for your videos, you could fit about 280 videos on there
Important Note:
The Mini only caches one playlist at a time (and you have endless storage in the XOGO Manager library) so even if you have loads of graphics, it's pretty unlikely that you will run out of space!