Ok, There are a number of options for these. and posted at various points already around tikiwiki.org
heres a summary and Im sure if you search here, you'll find details giving what to change in more details.
The 1Mb limit is likely because you have storage set to the MySQL database. Change this to file system.
You'll need to increase the PHP.ini file limit as thats set to 2Mb max_upload_size.
You might need to tweak apache's LimitRequestBody variable, thats sometimes set to 512k or 1Mb
Certainly larger files Id personally recomend storing in the file system. I dont like large blobs in the database as I feel thats easy corruption and will also slow down the database seeks.
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